documenting error handling

Author: docmarionum1

README.md

@@ -145,6 +145,22 @@ g.help('address')
 g.help('input')
 ```
 
+### Error Handling
+
+python-geosupport will raise a `GeosupportError` when Geosupport returns an
+error code.  Sometimes there is more information returned, in which case the
+exception will have a `result` dictionary.
+
+```python
+from geosupport import GeosupportError
+
+try:
+    g.get_street_code(borough='MN', street='Wort Street')
+except GeosupportError as e:
+    print(e) # 'WORT STREET' NOT RECOGNIZED. THERE ARE 010 SIMILAR NAMES.
+    print(e.result['List of Street Names']) # List of suggested alternate names
+```
+
 ## Development
 
 ### Running tests

geosupport/__init__.py

@@ -1 +1 @@
-from .geosupport import Geosupport
+from .geosupport import Geosupport, GeosupportError