[Invite Users]

- gem devise_invitable added.
- Creation of Users Invitation Controller with invite_params method redefined.
- Invite new users by email functionallity added.
- Invite users with logged users and not logged users created.

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[Invite Users]

- confirmation user invitation by email added.
- user sign out added in routes.
Merge pull request #15 from insignia4u/team-invite-users

[Invite Users]