Uniformative warning message

[mountainMath]

When requesting data for regions that are not covered by CMHC the code emits a warning message to report the 500 error. This should get changed to be more informative. One problem is that there could be many reasons for a 500 error, but the package could try and give more information on possible causes.

[mountainMath]

Example code to trigger this:

get_cmhc("Scss","Starts","Dwelling Type","Historical Time Periods", geo_uid="3519076")

(Trying to pull data for Chippewas of Georgina Island First Nation)

[mountainMath]

Addressed in #28.