added sections to Obtaining the Data, Exploring the Data and Preparing the data
added sections to Obtaining the Data, Exploring the Data and Preparing the data

sisiwei/ji-data-panel-2013,sisiwei/ji-data-panel-2013,sisiwei/ji-data-panel-2013,dwillis/hhdc-02-2014,dwillis/hhdc-02-2014