add PassJoin
add Edit Distance first attempt
add EditDistance class; extends PassJoin
Merge branch 'master' of https://github.com/sjyk/sampleclean-async into changes_Juan

Update code.
Merge branch 'master' of https://github.com/sjyk/sampleclean-async into changes_Juan

Merge with demo interface.
add EditJoin
add documentation for Edit Distance
Merge pull request #27 from sjyk/changes_Juan

Changes juan