ENH : added `phash` to ToolBase

Returns the SHA-1 of the tool name + current parameter values.

This can/should be overloaded by daughter classes to also mix
in information about versioning.
BUG : fixed typo + dtype issues
BUG : fixed sign error
BLD : added SNAPSHOT flag

having the version tagged wit the git build makes reloading
annoying as the egg infrastructure adds the install path (which
includes the git SHA) to sys.path python will only find the old version
of modules on `reload` even if a new version is installed.

The ability to tack git versions onto the version might still be
useful for building trackable snapshots.