Bump major version (2.5.0 -> 3.0.0)

Rationale: Breaking changes in API naming and versioning

* API names must now match the regexp `[a-z][a-z0-9]{0,39}`. This
  facilitates multiple APIs being allowed in a single service.
* API versions which are valid semver version strings will be parsed
  and the major version extracted as used in the path. This is a
  change from the previous behavior of using the whole string.

Author: inklesspen

endpoints/__init__.py

@@ -33,4 +33,4 @@
 from .users_id_token import InvalidGetUserCall
 from .users_id_token import SKIP_CLIENT_ID_CHECK
 
-__version__ = '2.5.0'
+__version__ = '3.0.0'