CBD-790 Build and run on Erlang OTP R16B

Upgraded mochiweb to version 2.4.2, so that it doesn't
require parametrized modules (removed from R16B) and
remove the unused etap_web and etap_request modules,
because they used parametrized modules.

This change still allows to build and run with Erlang
versions R14x and R15x.

Change-Id: Ib108468334b08aa0a29605d22c28a347fb5577d5
Reviewed-on: http://review.couchbase.org/25265
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Filipe David Borba Manana <fdmanana@gmail.com>
Reviewed-by: Volker Mische <volker.mische@gmail.com>