Remove the outdated PHPDoc documentation at doc/

The main API is presented in README.md, and all functionality can be
seen in the file tree on GitHub or directly in the IDE. Browsing a
rendered PHPDoc documentation is not a big benefit.

Author: alexander-nitsche

README.md

@@ -85,8 +85,9 @@ See the [demo.php](demo.php) file for a working example.
 
 ## `Syllable` API reference
 
-The following is an incomplete list, containing only the most common methods.
-For a complete documentation of all classes, read the generated [PHPDoc](doc).
+The following describes the API of the main Syllable class. In most cases, 
+you will not use any other functions. Browse the code under src/ for all 
+available functions.
 
 #### public __construct($language = 'en', string|Hyphen $hyphen = null)