Prevent span.help-inline around signup errors

In the *login view* an error looks like this:
```<div class="alert alert-error">Incorrect username, email or password.</div>```
In the *register view* it looks like this:
```<div class="alert alert-error"><span class="help-inline">The email field is required.</span></div>```
This was making my errors look weird.

This pull removes any default error wrappers to be more consistent with how the Login form displays error text.