I was using an old version and saw that 
```
r.contentEncodingEnabled = &enabled
```
Fix was added, however String() should be updated to also use a pointer receiver.

Per Golang Docs "In general, all methods on a given type should have either value or pointer receivers, but not a mixture of both."

…496)

* add test and fix for POST without body and Content-type, issue #492

* rm delete

* use exact matching of allowed domain entries, issue #489

* update doc, add testcases from PR conversation

* introduce AllowedDomainFunc #489

* more tests, fix doc

* lowercase origin before checking cors