Updates vars for button colors; adds buttons section to docs

Audited the color definitions in `_variables.scss`. Removed old unused
color defs which were left in there from old branding. Defined button
colors. Added descriptive text describing button usage and colors to
documentation.

It'll be nice to standardize mockups and comps to follow the same rules.
I added an .ase swatch file which can be downloaded from this site and
used in Photoshop, Illustrator, Fireworks, etc.

This file is built by the tasks/ase.php file. I included that file in
the repository for historical purposes. But its ugly to require yet
another language for the build environment, and to require hardcoded
variables. It'd be much nicer if this step could be automated, maybe as
a grunt task, which would read the colors from the variables.scss file...
Remove Less section from docs; update sass port info
Remove "lead" class from <p> starting "Brand colors"

As noted in https://github.com/janrain/bootstrap/pull/21#issuecomment-59858564,
using the "lead" class here is inconsistent.
Merge pull request #19 from janrain/thanj/buttons-documentation

Updates vars for button colors; adds buttons section to docs
Merge pull request #20 from janrain/thanj/remove-less-documentation

Remove Less section from docs; update sass port info
[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.