Write build information to "version" file and auto-fill error forms.

- Maven version and build date are now written to "res/version".
- The GitHub Issues form is auto-filled with error information if available. (reference: fluddokt/opsu@53fe3d9)

Signed-off-by: Jeffrey Han <itdelatrisu@gmail.com>

res/version

@@ -1,3 +1,6 @@
-#Mon, 03 Jun 2013 22:20:24 +0100
-#Sun May 11 20:17:03 BST 2008
+# opsu! build info
+version=${pom.version}
+build.date=${timestamp}
+
+# slick build
 build=237