update YCM
Squashed 'vim/bundle/ultisnips/' content from commit b272949

git-subtree-dir: vim/bundle/ultisnips
git-subtree-split: b272949b513b20a4b0d20e2cac06cf18cdaa068b
add ultisnips subtree
remove supertab
add configuration for using ultisnips with YCM
add golang snippets