Method 'getForms' so req.forms[this.formName] is overwritable.

- Means errorHandler values can be chanegd prior to response.
- Useful for returning empty password (login form) on error.
Merge pull request #32 from JoeChapman/feature/make-req.forms-overwritable

Method 'getForms' so req.forms[this.formName] is overwritable.