trivial documentation fix
Merge pull request #63 from tampakrap/readme_fix

trivial documentation fix
(refactor) Extract portage_version property

All types share this common property; it makes sense to coalesce them.
(maint) use `expect` over `lambda`
(refactor) extract portage_name parameter
Use ssl secured rubygems source
Merge branch 'refactor-extract_properties'
(maint) whitespace fix