use ssl:handshake on OTP-21+ instead of deprecated ssl:ssl_accept (#129)

* use ssl:handshake on OTP-21+ instead of deprecated ssl:ssl_accept

* add otp-21 to list of releases to test in travis

remove lager as a dependency (#125)

Merge pull request #112 from joedevivo/callback-mod-init-options

Callback mod init options

Merge pull request #107 from rslota/add_ping

Add ping support

Merge pull request #103 from posilva/feature/add_support_rebar2_projects

Add rebar.config.script deps for rebar2

Merge pull request #97 from tsloughter/master

use hex packages and add hex package metadata

Travis: kerl list installations

Merge pull request #72 from joedevivo/h2-rename

Renamed s/http2_/h2_

Updated hpack to 0.2.0

0.1.0 tagged release