runtime: Document python interface, clipboard and add intro doc

runtime/doc/nvim_clipboard.txt

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+*nvim_clipboard.txt*    For Nvim.					{Nvim}
+
+
+		 NVIM REFERENCE MANUAL    by Thiago de Arruda
+
+
+Clipboard integration for Nvim			       *nvim-clipboard*
+
+By default, Nvim has no connection to the system clipboard. Eventually that
+will be implemented by UI programs, which connect to Nvim via |msgpack-rpc|.
+
+Even though externalized UIs are not available yet, there's a workaround that
+enables clipboard usage through the python interface(which also uses
+|msgpack-rpc| and consequently can implement the clipboard methods required
+by Nvim): 
+
+- Make sure you follow the setup instructions in |nvim-python-quickstart|.
+- Install the `xerox` python module:
+  >
+      $ pip install xerox
+<
+- Create a ~/.vim/pythonx/nvim_clipboard.py file with the following contents:
+  >
+    import xerox
+     
+    class NvimClipboard(object):
+        def __init__(self, vim):
+            self.provides = ['clipboard']
+     
+        def clipboard_get(self):
+            return xerox.paste().split('\n')
+        
+        def clipboard_set(self, lines):
+            xerox.copy(u'\n'.join([line.decode('utf-8') for line in lines]))
+<
+This should enable the '+' and '*' registers. As an optional step, set the
+'unnamedclip' option to transparently access clipboard using the unnamed
+register. If you use the same |vimrc| for both Vim and Nvim, make sure you
+only set the option when `has('neovim')` is true:
+>
+    if has('neovim')
+      set unnamedclip
+    endif
+<
+
+==============================================================================
+ vim:tw=78:ts=8:noet:ft=help:norl:

runtime/doc/nvim_intro.txt

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+*nvim_intro.txt*    For Nvim.						 {Nvim}
+
+
+		 NVIM REFERENCE MANUAL    by Thiago de Arruda
+
+
+Introduction to Nvim						   *nvim-intro*
+
+This is an introduction new Nvim users. It is meant for experienced Vim users
+that want to get started with Nvim. For a basic introduction to Vim, see
+|help.txt|.
+
+For now, it is just an index with the most relevant topics/features that
+differentiate Nvim from Vim:
+
+1. Msgpack-RPC			|msgpack-rpc|
+2. Job control			|job-control|
+3. Python plugins		|nvim-python|
+4. Clipboard integration	|nvim-clipboard|
+
+==============================================================================
+ vim:tw=78:ts=8:noet:ft=help:norl:

runtime/doc/nvim_python.txt

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+*nvim_python.txt*    For Nvim.						 {Nvim}
+
+
+		 NVIM REFERENCE MANUAL    by Thiago de Arruda
+
+
+Python plugins and scripting in Nvim				  *nvim-python*
+
+1. Introduction			|nvim-python-intro|
+2. Quickstart			|nvim-python-quickstart|
+
+==============================================================================
+1. Introduction						    *nvim-python-intro*
+
+Through an external python interpreter connected via |msgpack-rpc|, Nvim
+offers some support for the classic |python-vim| interface. For now only the
+old Vim 7.3 API is supported.
+
+==============================================================================
+2. Quickstart					       *nvim-python-quickstart*
+
+If you just want to start using python plugins with Nvim quickly, here's a
+simple step-by-step:
+
+- Make sure python 2.6 or 2.7 is available on your `$PATH`
+- Install the `neovim` python package:
+  >
+      $ pip install neovim
+<
+- Add the following snippet to your `vimrc`, before any python plugins are
+  loaded:
+>
+  if has('neovim')
+    runtime! plugin/python_setup.vim
+  endif
+<
+Most python plugins created for Vim 7.3 should work after these steps.
+
+==============================================================================
+ vim:tw=78:ts=8:noet:ft=help:norl: