Updating README.md with info about how to authorize routes.

[wesleycsj]

After wasting some months and more hours reading code and some forums on internet. I found more people with the same question about authenticate function, and how to authorize routes. So, i decided to add this information to the README.

Checklist

• [ x] I have read the CONTRIBUTING guidelines.
• [ ] I have added test cases which verify the correct operation of this feature or patch.
• [ x] I have added documentation pertaining to this feature or patch.
• [ ] The automated test suite ($ make test) executes successfully.
• [ ] The automated code linting ($ make lint) executes successfully.

[coveralls]

Coverage remained the same at 97.619% when pulling a815bf8b82c63dca04476f5b294238faf5ce9cad on wesleycsj:master into 4d9fbefeba48164c43d5bde4e48ff57c2c37d372 on jaredhanson:master.