Need more tests.
More Header tests.
check equality of parsed Header types as well.
RawHeader hashcode is from its parsed form.
Change way of checking equality.
Implement header equality with ==.

Limitation: requires that headers are Products, and forbids headers
from defining equality semantics outside natural equality of
respective product elements.
Header equality cleanup.
Merge branch 'topic/header-java-equality' into develop

Conflicts:
	core/src/main/scala/org/http4s/Header.scala