Set git autocompletion and PS1 integration

1. Install Bash Completion

# Install bash completion
$ brew install bash-completion

# Install Homebrew's own completion script:
$ ln -s "/usr/local/Library/Contributions/brew_bash_completion.sh" "/usr/local/etc/bash_completion.d"

2. git_bash_prompt

# Add the following to your .bash_profile

# include $HOME/bin in your path
export PATH="$HOME/bin:$PATH"

# Set git autocompletion and PS1 integration
GIT_PS1_SHOWDIRTYSTATE=true
if [ -f `brew --prefix`/etc/bash_completion ]; then
  . `brew --prefix`/etc/bash_completion
fi
PS1='\[\033[32m\]\u@\h\[\033[00m\]:\[\033[34m\]\w\[\033[31m\]$(__git_ps1)\[\033[00m\]\$ '