Update build.gradle

org.robolectric:robolectric:2.3-SNAPSHOT is no longer available, changed to org.robolectric:robolectric:2.3 as it had a final release this week.
Update build.gradle

org.robolectric:robolectric:2.3-SNAPSHOT is no longer available, changed to org.robolectric:robolectric:2.3 as it had a final release this week.
Merge pull request #8 from RichardGuion/master

Robolectric 2.3 change