Removed unnecessary canvas skipPositioning flag.

The primary canvas uses position: absolute while the overlay canvas does
not.  This can cause the two to get out of alignment in rare cases when
floating elements are placed near the plot placeholder.  There doesn't
appear to be any reason why the overlay can't also be
absolutely-positioned, so I've just removed the flag entirely.

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.