contributors: added Bernardo Heynemann.
bump to 0.4.0.
repository: support a different host for readonly url

Fixes tsuru/tsuru#807.
webserver: bump to 0.4.1
travis: remove go 1.1 and add go 1.3
docs/config: add documentation for the readonly-host setting

Also improve the structure of the document.
requirements: remove fabric and circus