[JANRAIN-1223] Document class for dirty form state

Adds message to documentation mentioning the use of `.has-warning` to
indicated unsaved changes.
Update Bootstrap to v3.2

This fixes a problem we noticed with validation labels on `.sr-only`
elements. There are a few other changes in v3.2:
https://github.com/twbs/bootstrap/releases/tag/v3.2.0

Had to update the main scss file and the symlinks for fonts to reflect
the way TWBS repo structure changed.
Update state-danger variables for form states

Changed some of the contextual state-* variables so that
- all of these are being derived from the defined brand colors
- form error messages are displayed in a more sensible way

This undoes some styles which were added to make the panel headers look
stronger. Need to add a new helper class to manage that use case.
Custom helper classes for modals

Provides `bg-danger`, `bg-warning`, and `bg-info` classes for modals, to
style alerts.
Merge pull request #22 from janrain/thanj/dirty-state-documentation

[JANRAIN-1223] Document class for dirty form state