Use crypto:hash/2 instead of deprecated crypto functions
Use ssl:sslsocket instead of sslsocket{}
Bugfix: recognize upper/mixedcase transport values

Values for SIP transport were not recognized when they were not all
lowercase, e.g. if the peer would send "transport=TLS" it would not
work.
Remove dependency on ssl_internal.hrl

This include has changed as of R16B03 and depending on internal
structures of external applications leads to problems.  In this case,
nksip will fail to build on R16B03.
Merge pull request #22 from surik/fix_for_R16B

Fix for R16B
Merge pull request #23 from 2b-as/master

Bugfix: recognize upper/mixedcase transport values
Merge pull request #25 from danielwhite/remove-internal-ssl-dependency

Remove dependency on ssl_internal.hrl
Minor correction