*sh: set TERMINFO if appropriate

On my OS X box I'm running a mostly-vanilla set up, where "vanilla" is
defined as letting Homebrew install everything. On my CentOS box, in
contrast, I had to build a statically-linked tmux in order to get things
working with tmux 1.7, 1.8:

  https://wincent.com/wiki/Building_tmux_1.7_on_CentOS_5.8
  https://wincent.com/wiki/Building_tmux_1.8_on_CentOS_5.9

This means I have a statically-linked ncurses library, and it put a
bunch of terminfo files at $HOME/share/terminfo.

In order to be able to use italics in the terminal and Vim on this box,
I need to be able to install terminfo files there and the shell needs to
be able to find them. So, if that directory is present, set the TERMINFO
variable.

Signed-off-by: Wincent Colaiuta <win@wincent.com>
Zsh: try zsh's built-in Git completion

I've read reports that it might be better than the one Git itself
provides (which is actually a Bash completion script with a thin
wrapper). Let's try it out.

Signed-off-by: Wincent Colaiuta <win@wincent.com>
Add Solarized as a submodule

As a convenience for setting up the iTerm 2 color presets for solarized.

Signed-off-by: Wincent Colaiuta <win@wincent.com>
Remove unused terminfo files

To be replaced shortly with "italic" variants.

Signed-off-by: Wincent Colaiuta <win@wincent.com>
Add support for italic text

This requires a little bit of fiddling. On OS X:

  tic extras/xterm-256color-italic.terminfo
  tic extras/screen-italic.terminfo

Hack the Vim Solarized plug-in because it thinks that iTerm.app can't
support italics; it can, although at the time of writing you have to
compile your own:

  https://code.google.com/p/iterm2/issues/detail?id=391

Specifically, we move iTerm.app from the blacklist around line 140
(s:terms_noitalic) to the whitelist (s:terms_italic).

On CentOS, where I am using a statically linked ncurses library and all
my terminfo files are in $HOME/share/terminfo, in addition to running
the `tic` commands above, I had to export `TERMINFO` in my
.shells/exports file (see previous commits).

Also, the blacklist/whitelist trick is not enough, as TERM_PROGRAM is
not set over an SSH connection, so I hackedthe Solarized code evern
harder. Still not sure what the right move is there; probably to fork
and let g:solarized_italic trump anything else.

Finally, we set our terminal in iTerm 2 to xterm-256color-italic.

Signed-off-by: Wincent Colaiuta <win@wincent.com>