Getting a more compatible location for bash.

I don't need the features that are likely to be present in a custom bash
installation. Removing that requirement in the script makes it much more
portable.
Fixing the credential helper in git config

Previously, it'd work only on OS X and flash an error in Linux.
Including PATH cleanup code on linux systems
Fixing an error message
Making path to bash explicit on Linux

I could foresee possible scenarios where the absence of the full path might
cause problems.
Including ls options for linux

I wanted color in the output for ls in Linux. This was a good option I settled
on.
Get tmux to open new windows and panes in cwd

cwd-current working directory

The latest version of tmux (1.9) dropped that feature. The older version of tmux
(1.4) didn't have that feature either. Naturally, I was a little confused when
the tmux out on Linux didn't work of the box and an upgrade didn't help either.
I'm now including the officially recommended change in the tmux conf.
Getting the git_template in dot file collection

The git_template directory contains hooks that help with ctags. The install
script symlinks to the git_template directory.
Better error checking and directory creation

`mkdir -p` is a better of way of creating directories only when they don't
already exist.

Additionally, I had to check for whether a non-directory file by the same
name as the intended directory already existed. If so, the script had to abort
after emitting an appropriate message.

I also made progress towards a more modular organization of code in the
shell scripts.