Updated license headers for #805.

Added licensing information to each file's headers, along with some
minor cleanup.

Update timezone-js and Olson db; list sources in README.md.

Fixed global variables and missing seimcolons.

Adds arguments to the plotzoom event and fixes the bug where zooming could overrun a plot's pan range.

While Flot's codebase is currently a mish-mash of styles, we'd like to
move toward a unified style based on the jQuery core style guidelines.
Migration of existing code is scheduled for the 0.9 release.

Fix setting border color/width as an object.

* If either color or width is object, normalize the other to object
* Only draw each border if its width is greater than 0
* Set strokeStyle and lineWidth _before_ calling ctx.beginPath()

Return null from getSelection if there's no selection.

Fixed pie plugin 100% slice issues on IE7/8.

When a slice equals (or comes close enough that it is equal in
floating-point representation) 100% of the pie, it was no longer drawn
by Excanvas.  This is because of a long-standing issue where VML won't
draw an arc whose begin and end are the same.  Rather than some hack,
like adding/subtracting a small value, we'll simply draw two arcs for
every slice, with each covering half of the slice's angle.