Fix the reading of the localhost MTU in the HTTP tests

Sometimes the localhost interface has a different name from "lo",
this fix adds a helper function to read the MTU value when the
interface name starts with "lo".
Improve the detection of localhost interfaces for the HTTP test suite
Use ct_helper for retrieving the loopack interface MTU
Reword the clean erlang code part

We don't care about parameterized modules anymore. They're gone!
Greatly improve the guide introduction
Remove unknown keys from .app.src file
Minor corrections of the guide
Merge branch 'fix_docs' of git://github.com/pannonia-technologies/cowboy
Merge branch 'fix/http-tests-get-mtu' of git://github.com/soundrop/cowboy
Merge branch 'master' of https://github.com/extend/cowboy
Fix decoding of chunked body.

Previously cowboy_http:te_chunked/2 would enter an incorrect state if
it tried to parse an incomplete chunk when the length was known from the
partial chunk.

Previosuly cowboy_http:te_chunked/2 expected the trailing "\r\n" to
always be present if chunk body was present in the buffer. This is not
guaranteed and so this commit accommodates that situation.
Merge branch 'fix-chunked-req' of git://github.com/fishcakez/cowboy
Merge branch 'master' of https://github.com/extend/cowboy
Tweaks following feedback from Loic