Add same-codebase support for python 2.7.

When I opted for two codebases for python2/python3,
Send2Trash used C modules and it was easier to just have two
packages. With the ctypes version, supporting both python
versions becomes trivial and it's much more convenient to
merge them back into a single codebase.

I've only tested this code on Linux. I've converted plat_osx and
plat_win, but they only work theoretically.

README.rst

@@ -2,19 +2,25 @@
 Send2Trash -- Send files to trash on all platforms
 ==================================================
 
-This is a Python 3 package. The Python 2 package is at http://pypi.python.org/pypi/Send2Trash .
-
 Send2Trash is a small package that sends files to the Trash (or Recycle Bin) *natively* and on
-*all platforms*. On OS X, it uses native ``FSMoveObjectToTrashSync`` Cocoa calls, on Windows, it uses native (and ugly) ``SHFileOperation`` win32 calls. On other platforms, it follows the trash specifications from freedesktop.org.
+*all platforms*. On OS X, it uses native ``FSMoveObjectToTrashSync`` Cocoa calls, on Windows, it
+uses native (and ugly) ``SHFileOperation`` win32 calls. On other platforms, it follows the trash
+specifications from freedesktop.org.
 
 ``ctypes`` is used to access native libraries, so no compilation is necessary.
 
+Send2Trash supports Python 2.7 and up (Python 3 is supported).
+
 Installation
 ------------
 
-Download the source from http://github.com/hsoft/send2trash and install it with::
+You can download it with pip::
 
->>> python setup.py install
+    pip install Send2Trash
+
+or you can download the source from http://github.com/hsoft/send2trash and install it with::
+
+    >>> python setup.py install
 
 Usage
 -----
@@ -22,4 +28,4 @@ Usage
 >>> from send2trash import send2trash
 >>> send2trash('some_file')
 
-When there's a problem ``OSError`` is raised.
+When there's a problem ``OSError`` is raised.