Added appcast and release notes for the ShiftIt 1.6.6 release

Merge pull request #258 from kjrokos/master

Keeps the 1/2->1/3->2/3 window behavior, but resets the cycle anytime…

Merge pull request #243 from benpatterson/fix-readme-image

Fix image rendering in doc.

Merge pull request #217 from dawsonbotsford/patch-1

Move travis CI build badge from PNG to SVG

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Merge branch 'release/1.6.1'

Conflicts:
	README.md

Updated the WindowSizer related API.

1.4.1 release - rolledback the pref window UI