Load version from the file rather than by importing the module (which is subject to variance based on sys.path). Fixes #43.

Use 'is_valid' instead of simply 'valid' or 'check', which are less clear about the purpose of the method. Fixes AttributeError introduces in 0.9.2. Fixes #42.

Extracted hash-checking functionality into its own classes. Hashes are no longer checked when the proper pattern isn't detected. Fixes #42.

Re-wrote link inference to now respect specific patterns and generate links to known issue trackers.

setup.py now loads the version from setuptools/__init__.py, limiting the places where release.py must keep in sync.

Factored out the setuptools-specific code from release.py and moved the common functionality into jaraco.packaging. Use jaraco.packaging to enact releases.