Run tests on Travis CI

This commit adds configuration for building/installing RocksDB on Travis so the unit tests can be run.

Builds now take around 10 minutes. Also, I'm not sure how to configure it for OSX but I'm not sure if this is really important?

.travis.yml

@@ -5,9 +5,29 @@ rust:
   - 1.1.0
   - 1.2.0
 
-os:
-  - linux
-  - osx
+dist: trusty
+sudo: true
+
+addons:
+  apt:
+    sources:
+    - ubuntu-toolchain-r-test
+    packages:
+    - gcc-5
+    - g++-5
+    - libgflags-dev
+    - libsnappy-dev
+    - zlib1g-dev
+    - libbz2-dev
+
+install:
+  - curl -L https://github.com/facebook/rocksdb/archive/4.13.fb.tar.gz | tar xvz -C $HOME/rocksdb
+  - sudo INSTALL_PATH=/usr make -C $HOME/rocksdb/rocksdb-4.13.fb install-shared
 
 script:
-  - rustc -Z parse-only src/lib.rs
+  - cargo test
+
+cache:
+  directories:
+    - $HOME/.cache/
+    - $HOME/rocksdb/