Update vimrc

I think the NERDTree window should not resize between multiple toggles.  Makes it difficult to read the longer file names.
Merge pull request #76 from xiaogwu/master

Update vimrc
Merge pull request #77 from DirkR/installer_improvements

Check for git and vim before running the install.sh script.
Added sjl/splice.vim to package 'coding'
mattn/gist-vim depends on mattn/webapi-vim