Remove NPN support from OkHttp

Work in progress.

I see a new failure from a certificate pinning test but I don't
know why. Help solving this would be appreciated.

I also see failures before & after:
1) A failure from DisconnectTest
(https://github.com/square/okhttp/pull/1197 may fix that).
2) A failure from CallTest.doesNotFollow21Redirects_Async (timeout)

The maven changes should be treated with the contempt they deserve.
I mostly removed things I didn't understand and stroked maven until
it stopped squealing. The benchmarks / okcurl changes are a
particular mystery.

Tried with arbitrary versions of openjdk7 and openjdk8 I had
lying around. Behavior was the same across both (i.e. the same
failures).
Which comment / which aspect? 

Are you referring to the JavaDoc, or the "Java 8 and above only"...?