update author list; tidy generalize
generalize() now correctly checks the number of passed arguments. Added documentation. Fixed indentation.
Simplified code.
improve NA time warning
Added [[, [[<-, $ and $<- methods.
Merge remote-tracking branch 'upstream/master'
Updated selection methods.
add example, refresh example test output
update date
Merge pull request #1 from edzer/master

pull from Edzer