Grants access to:
* context match condition for context snippets (via snip.visual_text and
snip.visual_mode);
* pre/post actions (via same variable);
* context match condition to (!) lastly selected placeholder, so it is
possible now to use autotrigger snippets, that are activated by
simply typing letter while tabstop is selected;
* python interpolations to lastly selected placeholder;
It adds new type of flexibility, where just entered text can be
dynamically modified if some conditions are satisfied (e.g. dynamically
add line wraps).
The python module is now pulled in autoload/UltiSnips.vim. This means
that parsing of the .vimrc will only map the keys and set some options -
very cheap.
Unfortunately, the autocommands set up in plugin/UltiSnips.vim pulls in
the python code basically immediately still.
