QPF Tile Layer
Precip legend image
Use 4knam as default future tile type.
Add legends images:

- Lightning density (no layer yet)
- QPF
- Precip (was missing retina image)
Add LightningStrikeDensity tile layer
MockMapCanvas#jasmineToString

- to make failed tests easier to interpret
minor formatting changes
Update AerisMap attributes when created with a view instance

- Fixes #24
Update version to v0.7.12
Grunt `aeris.VERSION` task

- Updates build wrapper template to
  include a `aeris.VERSION` property definition,
  corresponding to the current version.
- Run task as part of 'build' task.
Update CHANGELOG
Fix example file Aeris cdn path
minor text change