Email validation message

[esron]

If the user enter an invalid email address in the login page it should show an red error message below the input.

If the email is valid but the server returned an empty object from the login route, it should alert the user that "No user was found" or "Email not registered".

[phuocding]

Could I fork the project and contribute to you?

[gab0gomes]

I think that especific messages are not a good pratices when validating login form's. The message should be something like "Invalid e-mail or password".

[gab0gomes]

Please, consider this on your PR @phuocding.