Move asyncio imports and update docs (#553)

Author: dbieber

docs/guide.md

@@ -589,6 +589,25 @@ default values that you don't want to specify. It is also important to remember
 to change the separator if you want to pass `-` as an argument.
 
 
+##### Async Functions
+
+Fire supports calling async functions too. Here's a simple example.
+
+```python
+import asyncio
+
+async def count_to_ten():
+  for i in range(1, 11):
+    await asyncio.sleep(1)
+    print(i)
+
+if __name__ == '__main__':
+  fire.Fire(count_to_ten)
+```
+
+Whenever fire encounters a coroutine function, it runs it, blocking until it completes.
+
+
 ### Argument Parsing
 
 The types of the arguments are determined by their values, rather than by the

fire/core.py

@@ -49,6 +49,7 @@ def main(argv):
   --trace: Get the Fire Trace for the command.
 """
 
+import asyncio
 import inspect
 import json
 import os
@@ -68,8 +69,6 @@ def main(argv):
 from fire import value_types
 from fire.console import console_io
 
-import asyncio  # pylint: disable=import-error,g-import-not-at-top  # pytype: disable=import-error
-
 
 def Fire(component=None, command=None, name=None, serialize=None):
   """This function, Fire, is the main entrypoint for Python Fire.

fire/inspectutils.py

@@ -14,14 +14,13 @@
 
 """Inspection utility functions for Python Fire."""
 
+import asyncio
 import inspect
 import sys
 import types
 
 from fire import docstrings
 
-import asyncio  # pylint: disable=import-error,g-import-not-at-top  # pytype: disable=import-error
-
 
 class FullArgSpec(object):
   """The arguments of a function, as in Python 3's inspect.FullArgSpec."""