Add module import validation

- Add new dev dependency grunt-es6-import-validate
- Add validate-imports run to buildScripts task
- Add configuration in tasks/options/validate-imports.js
- Add whitelist for resolver module
Fixed minor comment typo
Merge pull request #518 from existentialism/patch-1

Fixed minor comment typo
Merge pull request #502 from jgable/addImportValidate

Add module import validation
[fixes #521]
Rename _eak_seen to entries
Merge pull request #524 from teddyzeenny/entries

Rename _eak_seen to entries