Run the job when it's loaded.
Merge pull request #157 from luosheng/launchd

Ensure cow is loaded and run at startup in OS X Yosemite
Refactor proxy selection.
New load balance strategy: latency.

Select proxy with lowest connection latency.
Use Go 1.3 for Travis CI.
Sleep on error in accept loop.

Avoid flood of error logs upon too many open file error on Linux.
Get install directory from environment variable.
Bump version to 0.9.2
Allow @ and : inside password.
Describe customized http error code in sample config.
Add English version of sample rc.