A field can be required if all his dependencies are validated
remove dead code
Fix bug in case of required with precised dependencies
Fix line lenght
Merge pull request #1 from nicolaiarocci/master

update
Fix a bug in validation of empty field definitions
Add test for validation of empty field definition
Merge branch 'master' of github.com:hthieu1110/cerberus into hthieu1110-master
DRY and performance for #53
Merge branch 'hthieu1110-master'
Trong Hieu HA
Docs update for #53
Add 'versionchanged' tag.
Merge pull request #54 from girogiro/master

Fix validation of fields with empty definition
Fix validation of fields with empty definition
add `validator` rule for customized function
Docs update for `validator` rule