Initial creation of a feature to do social login

Works for LinkedIn and Facebook. Adding the rest of networks
should be pretty straight forward.

Ready for review as there are some bits that need to be changed.
Fixes after the review.

- Single quotes instead of double quotes
- Added quotes in the steps to surround "variables"
- Other minor changes
Merge pull request #1 from albertpastrana/base_structure_and_sample_test

Initial creation of a feature to do social login