Add function to iterate through object properties

- And return undefined if a supplied property does not exist within the object
- Or return the value of the final supplied property if it is defined
Add tests for checkProperties function
Rename, refactor property getter; add test

- Rename checkProperties to 'nestedValue'
- Use local var during loop instead of argument object
- Return an explicit undefined value if tested property doesn't exist
- Add test for empty propertyChain argument
Should ensure tests pass before pushing...
Tweaked JSDoc return types
Merge branch 'master' into deep-property-get

Conflicts:
	tests/runner/main.js
Merge pull request #6 from mobify/deep-property-get

Check whether a list of properties exists within a given object