[git] Use personal email address for commits

Because it's simpler to use one address everywhere.
[vim] Enable syntax highlighting for JSON
[vim] Enable syntax highlighting for Markdown
[vim] Use preferred Vundle syntax

Vundle now prefers the 'Plugin' namespace; the 'Bundle' namespace is
deprecated[1].

[1]:
https://github.com/gmarik/Vundle.vim/blob/master/doc/vundle.txt#L345-L369
[vim] Let Vundle manage updates to Vundle
[vim] Use Vundle to pull in Vim Solarized theme
[vim] Don't show Vim default mode indicator

This functionality is now provided by the Airline plugin.
[vim] Enable tagbar extension for Airline