.travis.yml: Add ccache

Author: zultron

.travis.yml

@@ -1,6 +1,14 @@
 sudo: required
 language: c++
-before_install: ./scripts/travis-install-build-deps.sh
+cache: ccache
+before_install:
+  # Clear ccache stats
+  - ccache -z
+  - ./scripts/travis-install-build-deps.sh
 script: ./scripts/travis-build-test.sh
+after_success:
+  # Show ccache stats
+  - ccache -s
+
 notifications:
     email: false