included ic7459 and ic74138
included new ic74138 and ic7445 using combinational.py
included ic74138 ic7459 and modified ic74138 and ic7445 using combinational.py
Added truthtable for ICs
Invalidlists defined during Initialisatn itself

For the 'truthtable()' method for ICs, it was necessary that the invalidlist be defines during initialisation of that IC.
Example for 'truthtable' method.
added tests for IC_7445_new,IC_7459,IC_74138,IC_74138_new
Pull changes from shrutig:ic2
Resolve merge conflict of PR https://github.com/BinPy/BinPy/pull/149
PEP8 fixes
PEP8 Fixes to series_7400_tests.py
PEP8 Fixes to series_7400.py
Corrected IC tests. Ordered IC classes. Removed the new tag
PEP8 and removed debug line
Merge pull request #3 from rvraghav93/shrutig-ic2

Shrutig ic2
Remove merge conflict
Add shrutig to AUTHORS
Merge pull request #209 from debugger22/shrutig-ic2

Shrutig ic2
Merge branch 'develop' of https://github.com/BinPy/BinPy into develop
Add missing names in AUTHORS
Merge pull request #167 from mohitgujarathi14/tt

Added Truthtable method for ICs
'Truthtable' method when applied can give the user a truthtable corresponding to the set of inputs and outputs pins specified by the user for a defined IC.
PEP8 fix