Add support for Secret Key

[asierraserna]

Hello!

In my sites I use the Secret Key, normally via Google Authenticator, to add an extra level of security.

From all my tests and what I have tried so far, com_api does not accept input of the Secret Key to grant access.

This causes that users using Authenticator will not get access through com_api

[asierraserna]

Hello @coolbung @parthlawate @haydenyoung and @vishal22 !

I solved this one with this pull, please take a look and let me know if it could be merged:

https://github.com/techjoomla/com_api/pull/132

Cheers!

[asierraserna]

I made #132 to correct this one, please check it out @coolbung