cowboy_protocol: accept host using ipv6 literal
add unit test for cowboy_protocol:parse_host/1
make cowboy_client:request() allow to override Host header

this will be used by tests
Add request body support for SPDY

And various other improvements following the addition of two tests.

New dependency cowlib that will gradually receive most of the parse
code from SPDY but also HTTP and its headers.
add some tests for Host header parser
Merge branch 'ipv6-literal' of git://github.com/yamt/cowboy
Fix specs for SPDY
Simplify the SPDY code by adding child management functions
Fix a badmatch issue when calling which_children on SPDY process
More SPDY code readability improvements