adds the ability to send the meta attribute in several calls that it was...

... left out on.

Pretty simple fix, there were several call (especially when using orders) that only allow specific options to be included. This simply adds the meta attribute to those allowed options.

Other calls simply pass the options directly to Balanced, so they were allowing the meta attribute to be assigned. 

I didn't include any tests for this, since there are no other examples of tests for optional attributes in there, but all the current test were still passing with this change.