chg: adopt now-standard __version__ type
chg: adopt now-standard __version__ type

This follows the modern convention that module.__version__ be a string.
For convenience, we will expose a version_info property which is the
`SetuptoolsVersion`-compatible parsed version which supports the PEP 440
options for handling pre/post-releases, local changes, etc.

toastdriven/pysolr,django-haystack/pysolr,toastdriven/pysolr,django-haystack/pysolr