Add tmux option 'allow-rename off'.

This option prevents program from changing window names.
Merge remote-tracking branch 'origin/master'
Add gitignore option for ignoring vim/spell/*.spl files.
Fix typo in vimrc comment.
Add choosing of YouCompleteMe Python interpreter.

The interpreter is chosen based on the operating system information.
This is done because YouCompleteMe works only with Python 2.
Add word plugin into the Vim dictionary.