issue 43. try ogr.GetUseExceptions

Use try: except: to catch the case where the installed version of OGR does not have GetUseExceptions. May want to add warning to the except clause.
Add old OGR warning and test Exceptions set.

Return test for gdal use exceptions already being set and add warning for old gdal/ogr versions without python exceptions.
Merge pull request #44 from NPounder/master

issue 43. try ogr.GetUseExceptions