Support Ubuntu 14.04 and Debian 8

Also use Test Kitchen to test the cookbook.

```
bundle install
bundle exec kitchen verify
```

See http://kitchen.ci/docs for more documentation

site-cookbooks/ipfs/.kitchen.yml

@@ -0,0 +1,17 @@
+---
+driver:
+  name: vagrant
+
+provisioner:
+  name: chef_solo
+
+platforms:
+  - name: ubuntu-14.04
+  - name: ubuntu-16.04
+  - name: debian-8.7
+
+suites:
+  - name: default
+    run_list:
+      - recipe[ipfs::default]
+    attributes: