Add .gitreview

Add a suitable .gitreview for using gerrithub; people should be able
to use 'git review -s' as expected.

Change-Id: I9686990b5616a6523cb0b2094170582899d0b9db

.gitreview

@@ -0,0 +1,4 @@
+[gerrit]
+host=review.gerrithub.io
+port=29418
+project=att-comdev/berth