Add integration tests and Travis config

Add Varnish config

Add backend to Varnish config

Add note about minimum Varnish version

Fix backend config and add debugging

Use PHP built-in webserver on Travis

Add base test class and Varnish tests

Use localhost

Add note on Varnish config

Debug PHP server start

Fix PHP server start
Merge pull request #19 from ddeboer/integration-tests

Add integration tests against Varnish on Travis