Add bobthefish theme.

![bobthefish](https://f.cloud.github.com/assets/53660/1221040/8b989ba0-26e4-11e3-94af-54adbb3fd620.png)

bobthefish is ported from a Bash prompt I used for years, and uses a Powerline segment function based on agnoster's.

### Features

 * A helpful, but not too distracting, greeting.
 * A subtle timestamp hanging out off to the right.
 * Powerline-style visual hotness.
 * More colors than you know what to do with.
 * An abbreviated path which doesn't abbreviate the name of the current project.
 * All the things you need to know about Git in a glance.
 * Visual indication that you can't write to the current directory.


### The Prompt

 * Flags:
     * Previous command failed (`!`)
     * Background jobs (`%`)
     * You currently have superpowers (`$`)
 * User@Host (unless you're the default user)
 * Abbreviated parent directory
 * Current directory or Git project name
 * Current project's Git branch (`⭠ master`) or detached head (`➦ d0dfd9b`)
 * Git status, via colors and flags:
     * Dirty working directory (`*`)
     * Untracked files (`…`)
     * Staged changes (`~`)
     * Stashed changes (`$`)
     * Unpulled commits (`-`)
     * Unpushed commits (`+`)
     * Unpulled *and* unpushed commits (`±`)
 * Abbreviated project-relative path