It can be useful to set up mappings that apply only during expansion of
a snippet. UltiSnips does this internally with the `_setup_inner_state`
and `_teardown_inner_state` methods.
This commit adds some `User` autocommands so that users of UltiSnips can
set up their own mappings and tear them down at the same time as
`_setup_inner_state` and `_teardown_inner_state`.
This is particularly useful for people who are writing their own
expansion and jump functions using `UltiSnips#JumpForwards` and
`UltiSnips#ExpandSnippet()` and friends. Here's an example from my own
dotfiles:
- 0664b627e7
- 3740c248ee
Using this approach I've been able to get rid of Supertab and have a
more nuanced autocompletion experience that works exactly as I'd like
with YouCompleteMe.
