UltiSnips 3.1

• This is the last release done by @SirVer. The new maintainer of UltiSnips
  is @seletskiy. The repository remains https://github.com/SirVer/ultisnips,
  so this should not affect any users. This is also the last release to be
  published on vim.org. Please follow the master branch on GitHub for the
  latest stable version.
• New option e: Context aware snippets. This gives very precise and
  powerful control over which snippet should be expanded depending on
  surrounding code. UltiSnips-context-snippets
• New option m: Trim whitespace in all snippet lines.
• Very powerful, freely configurable pre/post-expand and post-jump actions
  allow for transforming the buffer outside the snippet. UltiSnips-snippet-actions
• Automatic triggering of snippets without the need to press the expand
  trigger. UltiSnips-autotrigger
• Better error reporting for snippet errors including python stacktraces
  and listing of executed code.
• Undo is more granular. Each jump and expand is now a separate undo step.
• UltiSnips now emits autocommands on certain events. UltiSnips-custom-autocommands
• clearsnippets now clears all snippets below the current priority. This
  fits better with the priority system introduced in 3.0.
• snipMate snippets support can be disabled. UltiSnipsEnableSnipMate
• UltiSnipsEditSplit got a new value 'context'. UltiSnipsEditSplit
• Improved syntax highlighting for snippets filetype.
• Mappings and autocommands are now only established when needed, i.e. when
  a snippet is active. This boosts performance outside of snippets.
• New integration with Unite, TagBar, and deoplete.
• New Ctags configuration file for snippet definitions.
• Bug fixes, performance improvements, code cleanups and refactorings.
• No longer supports Vim < 7.4.