plyr should be import, not depend
clean up compiler warnings /unused vars
bind[] works with language objects and with ... lists.

Fixes #12 and #6
disregard, not working with ... yet. new tests for bind
vaguely unsatisfacotry $<- and [[<- for dots
Dots: expressions() and [[<-, $<- methods; bind works with ...
Merge remote-tracking branch 'remotes/origin/master'