Move elevation to core config and clean up HTTP mocking in tests (#2378)

* Stick version numbers

* Move elevation to core config

* Migrate forecast test to requests-mock

* Migrate YR tests to requests-mock

* Add requests_mock to requirements_test.txt

* Move conf code from bootstrap to config

* More config fixes

* Fix some more issues

* Add test for set config and failing auto detect

homeassistant/core.py

@@ -681,6 +681,7 @@ class Config(object):
         """Initialize a new config object."""
         self.latitude = None
         self.longitude = None
+        self.elevation = None
         self.temperature_unit = None
         self.location_name = None
         self.time_zone = None