update router to check req.url matched path

[twhtanghk]

For special case with req.url 'http://host/user/vm/counter' and

router =
  '/vm/': 'http://192.168.1.1:8000'
  '/user/': 'http://192.179.1.1:8001'

Router would forward the request to 1st matched handler instead of the expected 2nd handler. This pull request is to ensure the matching to the first character of path or hostAndPath. Please review.

[coveralls]

Coverage remained the same at 96.97% when pulling f540fad on twhtanghk:master into cb5e084 on chimurai:master.

[coveralls]

Coverage remained the same at 96.97% when pulling f540fad on twhtanghk:master into cb5e084 on chimurai:master.

[chimurai]

Hi. Thanks for the PR.

Think the fix looks valid.

Can you fix the code warnings and provide a test plan?

https://github.com/chimurai/http-proxy-middleware/blob/master/test/unit/router.spec.js