Update verifications controller and add instruction to README

[hummusonrails]

In this PR I've addressed two areas:

• Fixed the Nexmo API syntax to correctly verify a user in the verifications_controller.
• Updated the README to include the rake db:migrate step in the installation, since without it the user will encounter an error when attempting to boot up the server for the first time.

[lornajane]

@benhayehudi , this looks valuable to me. Who can review this and get it accepted?

[hummusonrails]

@benhayehudi , this looks valuable to me. Who can review this and get it accepted?

Wow, haven't seen this in a while! Looping in @fabianrbz to review.

[fabianrbz]

@benhayehudi @lornajane it looks good to me, but i don't understand where the changes are coming from. Was the controller broken and this fixes it? or did we update the nexmo gem?

[hummusonrails]

@benhayehudi @lornajane it looks good to me, but i don't understand where the changes are coming from. Was the controller broken and this fixes it? or did we update the nexmo gem?

Yep, to both questions. I created this it looks like the first week I joined the team.

[fabianrbz]

@benhayehudi should we update the Gemfile.lock or does the specified version support this change?