Added Multiplexers and Demultiplexers

- Added multiplexer IC74152, IC74151A ,IC74153
- Added tests and examples for IC74152, IC74151A ,IC74153
- Added demultiplexer ICs 74138 ,74139 ,74155 ,74156 
- Added tests and examples for IC74156, IC74155, IC74139 ,IC74138
- Deleted series_7400_tests.py since ics_tests.py already existed
- Updated ics_tests with complete tests
- Updated .travis.yml