SPARK-1102: Create a saveAsNewAPIHadoopDataset method

https://spark-project.atlassian.net/browse/SPARK-1102

Create a saveAsNewAPIHadoopDataset method

By @mateiz: "Right now RDDs can only be saved as files using the new Hadoop API, not as "datasets" with no filename and just a JobConf. See http://codeforhire.com/2014/02/18/using-spark-with-mongodb/ for an example of how you have to give a bogus filename. For the old Hadoop API, we have saveAsHadoopDataset."

Author: CodingCat <zhunansjtu@gmail.com>

Closes #12 from CodingCat/SPARK-1102 and squashes the following commits:

6ba0c83 [CodingCat] add test cases for saveAsHadoopDataSet (new&old API)
a8d11ba [CodingCat] style fix.........
95a6929 [CodingCat] code clean
7643c88 [CodingCat] change the parameter type back to Configuration
a8583ee [CodingCat] Create a saveAsNewAPIHadoopDataset method