tagging 5.0.6; fixes DiffSK#59

Merge pull request DiffSK#57 from DiffSK/master

release 5.0.5

fixes DiffSK#52 - tagged 5.0.4

issue DiffSK#20 - needed to add _version to modules, and made __versi…

…on__ a simple import since we're not use a package

updating version numbers for 5.0.2 tag

fixes DiffSK#22

corrected badge URL