Merge pull request #54 from kristian-puccio/master

fixed validation for checkboxes
added the example in documentation for rails field convention
Fix npm install instructions

The instructions to `npm install grunt --save-dev` and so on for each dependency
are incorrect (even though it works).

That command is for installing a dependency (locally, inside
`./node_modules`) and (with the `--save-dev` flag) writing that dependency to the
`package.json` file.  So this can be used the first time you add a new dependency,
but isn't meant to be used again every time.

Because the dependencies are listed in `package.json` all you need to do to install
them is `npm install`.  You also never need admin rights to do this because it
installs them to `./node_modules` (npm will only install globally with the -g flag,
which is only meant for installing executables, not project dependencies). :)
Update callback.js
Add Danish zip code validation
#44: Deferred experimental
#44: Fix isValid() method
#53: Fix notEmpty validator for radio and checkbox
Merge pull request #62 from iplus/patch-1

Update callback.js
#62: The callback validator passes wrong parameter
Update different and identical validators due to validator.getFieldElements() modification
Merge pull request #60 from vaz/patch-1

Fix npm install instructions
#71: Show all errors
Live validating option
Fix submitHandler example due to validator.getFieldElements() changes
#44: Implement custom submitHandler
Submit form when all validators are completed and the form is valid
#73: Describe which version should be included in the Usage section
Merge pull request #64 from emilchristensen/feature_dk_zip

Add Danish zip code validation
#64: Support Danish zip code