add submodule slide1, slide2 for ETL and update helper functions

resolve #67
update tested slides
add url for visualization
add document for open slides for ETL1 and ETL2
Merge pull request #68 from wush978/split_ETL_slides

Split etl slides
Merge branch 'master' into add_vis1
Merge pull request #71 from wush978/add_vis1

Add vis1