Added new modules for battery status, makefile, foreground jobs, made modules reorderable, plus other fixes and upgrades

Hello,

I've been using your git-prompt for a while, adding new modules and features from time to time.
A few days ago I found your github, so I decided to fork and add my changes so that they can be merged back to the main repo.

Rationale for the new features:
- when I'm on a laptop, I want to know how much battery life still remains - this information is displayed by Unicode bar-chart drawing characters to save space.
- I usually have several tabs open in gnome-terminal, and some of the shells run programs in the background (like editors or number-crunching scripts). I like to be reminded not to close these tabs because I'd lose the background processes with them.
- If a project has a makefile (as most software projects do), I like to be able to tell with a glance whether the executables are up-to-date or I have to remake them.

Apart from these, I made the order of modules configurable and fixed a few minor things.