Merge pull request #1416 from citusdata/test_cache

Use cached PostgreSQL build to reduce testing time

.travis.yml

@@ -1,7 +1,10 @@
 sudo: required
 dist: trusty
 language: c
-cache: apt
+cache:
+  apt: true
+  directories:
+  - /home/travis/postgresql
 branches:
   except: [ /^open-.*$/ ]
 env:
@@ -14,7 +17,7 @@ env:
     - PGVERSION=9.5
     - PGVERSION=9.6
 before_install:
-  - git clone -b v0.6.1 --depth 1 https://github.com/citusdata/tools.git
+  - git clone -b v0.6.2 --depth 1 https://github.com/citusdata/tools.git
   - sudo make -C tools install
   - setup_apt
   - curl https://install.citusdata.com/community/deb.sh | sudo bash