Html Table Extractor Versions Save

• fix bs version issue

• custom file name write_to_csv
• loosen the requirement for bs4 to be >=4
• fix a corner case when a table string is passed in with an id

1. Use travis for auto-testing framework
2. Fix a bug in py3 that uses unicode

add a new function to write to csv file allow transformer in init

change the output of html table extractor

mainly update readme

first runnable version