Merge pull request #333 from maurer/cache

Enable caching of built deps

Author: ivg

.travis.yml

@@ -2,6 +2,11 @@ language: c
 install: wget https://raw.githubusercontent.com/ocaml/ocaml-travisci-skeleton/master/.travis-opam.sh
 script: bash -ex .travis-opam.sh
 sudo: false
+cache:
+  directories:
+    - $HOME/.opam
+  before_cache:
+    - rm -rf $HOME/.opam/log
 addons:
   apt:
     sources: