Partially revert e675625.

It causes problems with Travis CI builds because travis checks out the branch which might have newer commits and not find our particular commit.

Author: sledgehammer999

.travis.yml

@@ -1,9 +1,6 @@
 language:
   - cpp
 
-git:
-  depth: 1
-
 env:
   matrix:
     # Uncomment when Travis upgraded "Ubuntu 12.04 LTS" to a newer version whose repo will have a more up-to-date libtorrent package