Merge pull request #479 from portertech/beta

[beta] need Oj compat mode, beta version bump
Merge pull request #481 from portertech/beta

[beta] new oj release, fixed rb_infinity on centos
[keepalive] send ok keepalive check results, fixed history & flap detection
[keepalive] adjusted keepalive ok check output
Merge pull request #482 from portertech/keepalive

Improved stale client checking, fixed keep-alive check history & flap detection.
[beta] beta version bump