Login subscribe validation

fixes #141
From what I read and know, the best way to test whether an email is valid or not is to just check the presence of ``@``. Anything else would be too restrictive and could make some very specific emails as false negatives.
The best way is still to send a verification email to it.
> [problem overview](http://stackoverflow.com/questions/201323/using-a-regular-expression-to-validate-an-email-address?page=1&tab=votes#tab-top) and [simple solution](http://programmers.stackexchange.com/questions/78353/how-far-should-one-take-e-mail-address-validation)