Add removeProperty unit test
Add removeProperties method to element wrapper
Merge pull request #52 from jcamins/removeproperties

Add removeProperties method to element wrapper
 - split off removeProperty tests
 - unwrap objects passed to start
 - standardize wrap and unwrap methods
 - updating npm version
Correct calling convention for _ifIsNull in pipeline wrapper
JS primitives can't have properties

In some unidentified situations, a JS primitive will be passed to
_isType, which causes an error.
Wrapping null values shouldn't crash program