Fix issue #541: Add TortoiseGit config for bugtraq and icon

Extracting image from "progit2\book\cover.png", then using that extracted image to make "Pro.ico" by using http://converticon.com/.

File ".tgitconfig" is copied from TortoiseGit repository and modified for this repository.

Author: YueLinHo

.tgitconfig

@@ -0,0 +1,6 @@
+[bugtraq]
+	url = https://github.com/progit/progit2/issues/%BUGID%
+	logregex = "[Ii]ssues?:?(\\s*(,|and)?\\s*#?\\d+)+\n(\\d+)"
+
+[tgit]
+	icon = Pro.ico