Add function dropNA(Axis pattern) for user to choose which pattern(row or
column) to use.
fix style
add test unit for dropNA()
Merge pull request #11 from ljzzju/addMethod

Add function dropNA(Axis pattern) for user to choose which pattern(row o...
update ddf-env
remove hardcode in spark/conf/ddf-env.sh
add mem-size-detection.sh to detect memory size
It will never go here, so delete it.
Merge pull request #16 from DoingDone9/master_issue

It will never go here, so delete it.
Delete else{ //TODO }
Merge pull request #21 from DoingDone9/master_issue_03

Delete else{ //TODO }
Merge pull request #1 from ddf-project/master

merge DDF to my