Add proxy mode.
Proxy promotion.
Add automatic node promotion / demotion.
fix(README): remove the drone.io badge

the drone.io badge is either cached wrong by github or links to a wrong version when we build a branch, just remove it.
fix(discovery): remove its own address from peer list to join
fix(tests/multi_node_kill_all_and_recovery): wait for cluter to build over
fix(transporter): CancelRequest doesn't work on HTTPS connections blocked

Currently this is a workaround. And it should be fixed in Go1.3.
chore(server): remove useless CancelWhenTimeout

Setting request timeout is covered by go-httpclient now.
Merge pull request #598 from unihorn/19

fix bugs that are found in issue #579
Add auto-demotion after peer inactivity.
fix(Documentation/*): fix various typos
Merge pull request #604 from ccding/master

fix trivial issues as I see them
Check for peer before demotion.
Fix JoinCommand comment.
Minor fixes.
feat(scripts/test-cluster): create three proxy nodes

This uses some sleep hackery to make sure that window 1 has followers
and window 2 has proxy machines. Seems to work!
docs(errorcode.md): add the EcodeRootROnly error
Add PHP library.

We implement the api client useing php.
Merge pull request #612 from congpeijun/master

Add PHP library.
Merge pull request #607 from Asmod4n/patch-1

Added Error 107 to Documentation