enable configuring of nodejs https options
Polish #74 from @wwwdata

- renamed 'request.httpsOptions' to 'request.mixins' for consistency with the XHR client
- added tests, now testing https requests
- added property to client docs
- added to README release notes
Support Browserify

- avoid references to 'this' as the global object, as browserify makes
  this undefined instead of the global
- also removing unchecked references to 'window'

See: https://github.com/substack/node-browserify/issues/372
Release v1.1.1
Bump version for development
Improve testability

- decrypt SAUCE_ACCESS_KEY so pull requests can be fully tested
- split Sauce, Node and linting into different travis test targets