disable the JS plugin by default

Merge pull request fagongzi#132 from caozhipan/fix-activeQPS-zero

setDeadLine & retry

dev: add option for setting host

fix: x-forwarded-for header

Merge pull request fagongzi#120 from domgoer/master

fix: use unsupported loadbalance will cause nil pointer

fix: missing header when copying request

fix: caching deadline duration

fix: analysis for api circuit breaker

docs: update docs

fix: update go version to 1.11