.bashrc: Don't check for $STY in settitle()

Update settitle() to always echo escape sequence regardless of
whether $STY is set. $STY is only set on immediate screen shells;
when ssh'd to remote hosts $STY won't be set there.
.bashrc: Alias diff="git diff --no-index"

Use "git diff --no-index" as a prettier "diff" alternative (if
available) since it supports nice colored output (via .gitconfig).
.vimrc: Tweak StatusLineNC colors

Tweak StatusLineNC (inactive buffer when in split-mode) colors to be
higher contrast based on my new solarized-ansi color theme.
bin/ack-wrapper: Use ack-wrapper

Creating a bridge script for allowing directory-level additional
.ackrc settings but without overriding the default $HOME/.ackrc
settings. This allows for directory/project-specific .ackrc files,
e.g. for project-specific --ignore-dir settings.