Minor cleanup of text-style color defaults.
Give tick labels the 'tickLabel' class.

The tickLabel class is deprecated in favor of flot-tick-label, but we'll
continue to use it until the release of version 1.0.0, for
backwards-compatibility.
Updated the API docs for axis text changes.
Add back legacy styles for tick label containers.

These styles are deprecated, but we'll continue to use them until the
release of version 1.0.0, for backwards-compatibility.
Updated NEWS for axis text changes.