Checks if field exists (is not null, but can be empty).
Merge pull request #24 from lferro9000/exists_validator

Checks if field exists (is not null, but can be empty).
Fix callable function name if not callable.
Merge pull request #25 from lferro9000/callable_error

Fix callable function name if not callable.
Rewritten handling of callback validation.
Fixed big regression on easy redirects and routing in general.
Correction of variable used on apps/appname/conf.php.

Update of helloworld example on readme file to reflect current Assegai version.
Merge pull request #26 from lferro9000/docs_update

Correction of config file and readme.md.
Improved error handling.