Update README with two caveats for Mac builds (case-insensitive FS and linker OOM with noopt).
Fixing formatting in README.md.
Removing TODOs accidentally left in README.
Merge pull request #255 from jlebar/readme-updates

Update README with two caveats for Mac builds (case-insensitive FS and l...
Add support to helix.
Add Nexus 4 and JB emulator build support
Run b2g-info when doing a memory report with get_about_memory.py.