new rule: requireHyphenBeforeDescription

#50

This might need some more tests?

I'm assuming most people want the space so its like ` - description` not ` -description`

so it works like ` if (tag.description.substring(0, 2) !== '- ') {` 


[This test](https://github.com/jscs-dev/jscs-jsdoc/blob/master/test/lib/rules/validate-jsdoc/check-param-names.js#L196) checking location.