Implement captcha

[vgeorge]

When the repcatcha strategy is implemented at the backend, the web app will need a captcha component.

Depends on: mapascoletivos/api#51

[vgeorge]

@bwstefano this feature is live at the staging website:

http://mapascoletivos.surge.sh

Could you please review if captcha is working well at user registration and password registration?

[bwstefano]

User registration isn't working. If I click on Register nothing happens at first time. If I click on it again, I get the following error message: user.create.error.missing.captcha

[vgeorge]

@bwstefano the problem is not related to the captcha, but a wrong mailer setting. I've fixed it and disabled e-mail confirmation at staging because of #39. Can you review the captcha again?

[bwstefano]

It's now working. As expected, I didn't receive a confirmation email. I did receive an email when filling the "Forgot my Password" form, though without a working link. Anyway, captcha worked fine and I wasn't able to create an account without filling it.