Update SparkleAboutController.cs

Fixed link to the authors.txt file.
Merge pull request #1513 from cebe/patch-1

Update SparkleAboutController.cs
Add Bountysource badge to README

Because you have some open bounties, we thought you might want to display this badge in your README!
Merge pull request #1523 from bountysource-support/patch-1

Add Bountysource badge to README
Merge pull request #1 from hbons/master

Upstream Changes