Update README.md
Feature: Infer the URL from the class name

If the `url` class method is not called on a class that extends Rapidash::Base
then the class name will be downcased and used as the url.

    class Users < Rapidash::Base
    end

    client.users! # Get from /users

Any module defined will be ignored and only the class name used.
Update README.md

Add Travis CI button
Merge branch 'master' of github.com:Gazler/rapidash

Conflicts:
	README.md

Note to self, stop forgetting to pull after using the Github web interface