update license to Apache 2.0
comment out unused script
add method na.omit()
Update ddf.R

change the parameter representation in Method na.omit()
Update ddf.R

undate
Update

update
Update ddf.R
Update ddf.R
Update ddf.R
Merge pull request #43 from ljzzju/na.omit

add method na.omit()
Merge branch 'master' into ddf-sparksql-1.1.0

Conflicts:
	pom.xml