Clone 1000 commits on Travis CI (#2124)

The previous failure we saw was because the most recent annotated tag
did not exist in the previous 50 commits. In my experience we've gone
about ~300 commits between tags, so I believe 1000 to be safe, but know
100 will not be.

.travis.yml

@@ -5,6 +5,9 @@ branches:
     - master
     - /^test.*$/
 
+git:
+  depth: 1000
+
 os:
   - linux
 sudo: required