Upgrade fixkey to 0.3.4.
Move the definition of UltiSnips#FileTypeChanged to prevent an error.

Recently, Neovim started reporting an error since this function was
being defined in our vimrc but has a prefix of `UltiSnips#`.  This
moves the definition to after the plugin loads, and checks
g:EnableUltiSnips to define the dummy function.
Merge branch 'filetypechanged-fixup' of https://github.com/jszakmeister/vimfiles