Move the vim example to a separate plugin folder

When Powerline is installed as a package in the system-wide
site-packages folder it can easily be enabled by adding a simple python
statement to the user's vimrc file.

Otherwise it can be added by doing a :source
path/to/plugin/vim/powerline.vim in vimrc, but the other way of doing it
works without specifying the full path as long as Powerline is installed
somewhere in sys.path.

MANIFEST.in

@@ -1,2 +1,3 @@
 recursive-include powerline *.json
+recursive-include plugin *.vim
 exclude powerline/tests/*.xml

plugin/vim/load_vim_plugin.py

@@ -0,0 +1,4 @@
+import os
+import vim
+
+vim.command('source ' + os.path.join(os.path.abspath(os.path.dirname(__file__)), 'powerline.vim'))

plugin/vim/powerline.vim

@@ -1,5 +1,9 @@
-" Powerline vim example
-" Run with :source %
+" Powerline vim plugin
+"
+" If Powerline is installed in a Python search path, load the plugin by
+" adding the following line to your .vimrc:
+"
+" python import plugin.vim.load_vim_plugin
 
 python import sys, vim, os
 python sys.path.append(vim.eval('expand("<sfile>:h:h:h")'))
@@ -38,4 +42,3 @@ augroup Powerline
 	autocmd BufEnter,BufWinEnter,WinEnter * let w:current = 1 | call s:UpdateAllWindows()
 	autocmd BufLeave,BufWinLeave,WinLeave * let w:current = 0
 augroup END
-" vim: ft=vim noet