Add `__version_info__` derived from `__version__`

This might be tuple of more than two values (major and minor
version) if commits have been made after a release.

datasette/__init__.py

@@ -1,7 +1,7 @@
-from datasette.version import __version_info__, __version__  # noqa
 from .hookspecs import hookimpl # noqa
 from .hookspecs import hookspec # noqa
 
 from ._version import get_versions
 __version__ = get_versions()['version']
 del get_versions
+__version_info__ = tuple(__version__.split("."))

datasette/version.py

@@ -1,2 +0,0 @@
-__version_info__ = (0, 22)
-__version__ = '.'.join(map(str, __version_info__))