Web test creation

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #29 
| License       | MIT
| Doc PR        | nothing changed

I got the web tests run. All current behavior is tested now. Fixed a little bug with non existing configs for `sonata_seo` too. 
Created fixtures to request with content and route. Created a TestController for rendering a test template. 
Let tests run for http state, content title-tag, meta-tags and canonical link, would like to test everything with different configs to get the redirect case too. Any ideas?