Improve "Python not found dialog"

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| <img width="602"src="https://cloud.githubusercontent.com/assets/1570168/11857669/2a2dc854-a40f-11e5-99a4-cf29366c7885.png"> |

Rationale and changes:
 - Permanent actions without a clear "undo" button are confusing for new users.
   Change: The "Don't show this again" button is moved to a more "dangerous" location (where "Don't Save", a destructive action, normally appears)

 - Modals can get really annoying, and some people will expect to open files with badly configured Pythons and not be faced with a modal.
   Change: Add an setting "suppress_python_not_found_error" to permanently turn off modals
   Change: Always error to console, even if modal turned off, for advanced users

 - Change: aesthetic changes to dialog

 - Change: add link to documentation

 - Users might not know who is responsible for the dialog
   Change: Add plugin name in dialog

Author: szhu

README.markdown

@@ -14,6 +14,8 @@ I also added a lot caching throughout the underlying Rope library which improved
 Configuration
 -------------
 
+## Python location
+
 The only necessary configuration is pointing SublimePythonIDE at the correct Python interpreter to use.
 There are four mechanisms for detecting Python that are used in the following order:
 
@@ -40,6 +42,13 @@ The option "python_interpreter" can be set in the projects settings (Project->Ed
 
 This is also the way to select a virtualenv (point it to the interpreter in the venv) and thus get the completions/definitions for you project working.
 
+To suppress the "Could not find Python dialog", save the following setting:
+
+    "suppress_python_not_found_error": false,
+
+
+## Imports location
+
 SublimePythonIDE will also look up imports relative to the project root directory (the top directory of your project).
 
 In cases where the project directory is outside of your root python module, you may optionally set a custom source root directory in the project settings:

sublime_python.py

@@ -358,24 +358,48 @@ def proxy_for(view):
 
 
 def show_python_not_found_error(python_detectors):
-    if LAST_ERROR_TIME is None or (time.time() - LAST_ERROR_TIME > 10.0):
-        do_not_show_again = sublime.ok_cancel_dialog("""
-Could not detect python, please set the python_interpreter (see README) using an absolute path or make sure a
-system python is installed and is reachable on the PATH. Here is the order in which paths are tried:
-
- - By "python_interpreter" Sublime settings: %r
- - By auto-detecting venv: %r
- - By #! (shebang) line in this file: %r
- - By auto-detecting system Python: %r
-
-We use the first non-None value and ensure that the path exists before proceeding.
-""" % tuple(d() for d in python_detectors), "Do not show again")
-
-        global LAST_ERROR_TIME
-        if do_not_show_again:
+    global LAST_ERROR_TIME
+    if LAST_ERROR_TIME is not None and (time.time() < LAST_ERROR_TIME + 10.0):
+        return
+    LAST_ERROR_TIME = time.time()
+
+    msg = (
+        "SublimePythonIDE: Could not find Python.\n"
+        "Make sure Python is accessible via one of these methods:\n"
+        "\n"
+        " \xb7 From SublimePythonIDE settings:\n"
+        "   %r\n"
+        " \xb7 From venv settings:\n"
+        "   %r\n"
+        " \xb7 From #! (shebang) line in this file:\n"
+        "   %r\n"
+        " \xb7 From system Python (via $PATH):\n"
+        "   %r\n"
+        "\n"
+        "We use the first non-None value and ensure that the path exists before proceeding.\n"
+        % tuple(d() for d in python_detectors)
+    )
+
+    if not get_setting("suppress_python_not_found_error", False):
+        result = sublime.yes_no_cancel_dialog(
+            msg +
+            "\n"
+            "\"Do Not Show Again\" suppresses this dialog until next launch. "
+            "\"More Info\" shows help for configuring Python or permanently suppressing this dialog."
+            , "More Info", "Do Not Show Again"
+        )
+        # In case the user takes more than 10 seconds to react to the dialog
+        LAST_ERROR_TIME = time.time()
+        if result == sublime.DIALOG_YES:
+            import webbrowser
+            webbrowser.open("https://github.com/JulianEberius/SublimePythonIDE#configuration")
+        elif result == sublime.DIALOG_NO:
             LAST_ERROR_TIME = float("inf")
-        else:
-            LAST_ERROR_TIME = time.time()
+
+    raise OSError(
+        msg +
+        "More info: https://github.com/JulianEberius/SublimePythonIDE#configuration"
+    )
 
 
 def root_folder_for(view):