Miscellaneous grammatical & consistency changes

- Various grammatical changes and rephrasings
- Capitalize names of VCSes and "Bash"
- Standardize references to project name ("Liquid Prompt")
- Use title casing in README section headers
- Use multiple list-levels in README where appropriate
- Fix code block in pull request instructions in CONTRIBUTING
Add pmset-simulator to simulate battery info on MacOS X

https://github.com/nojhan/liquidprompt/issues/326
pmset-simulator: fix tabs

Thanks to @MafooBristol in
https://github.com/nojhan/liquidprompt/issues/326#issuecomment-66104427
Battery/MacOS X: improved parsing

Parsing improved (faster, stricter), manually tested with pmset-simulator.
TODO: write automated tests.

https://github.com/nojhan/liquidprompt/issues/326
Battery/MacOS X: fix pmset parsing for tabs

See
https://github.com/nojhan/liquidprompt/issues/326#issuecomment-66104427
pmset-simulator: add state 'attached'

See
https://github.com/nojhan/liquidprompt/issues/326#issuecomment-66120495
pmset-simulator: strong quoting of here-docs
Battery/MacOS X: strong quoting for status value

The status value may be 'AC attached', so we have to properly quote to
avoid spaces.
Battery/MacOS X: replace fuzzy matching with strong matching

As we now have a strong simulator, we can replace fuzzy matching on
status values with exact matching.