Honor TZID when evaluating UNTIL [Issue 37]

[Ferix9288]

Issue: #37

Easy fix where I call StrToROptionInLocation with defaultLoc instead of just StrToROption that defaults to UTC.

		case "RRULE", "EXRULE":
			rOpt, err := StrToROptionInLocation(rule, defaultLoc)
			if err != nil {
				return nil, fmt.Errorf("StrToROption failed: %v", err)
			}

Other notable changelog:

• Updated TestStrSet and TestRFCSet so that the UNTIL now respects UTC or NY timezone
• Added a testcase and imported assert and require library. I'm ok with rejecting this added testcase.

[coveralls]

Coverage remained the same at 99.663% when pulling 3c634b3 on Ferix9288:fix_issue_37 into c4b1bf2 on teambition:master.

[Ferix9288]

Never mind. Looks like this is intentional behavior based on the RFC spec.