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.
In Readme, Added instructions to help dev pass the pep8 tests
Fixes #188
Merge branch 'develop' into addpep8
Merge pull request #189 from rajat974/addpep8

Fixes #188
Merge pull request #186 from rvraghav93/autopep8

Updated the readme with instructions to help devs pass the pep8 tests.
Updated README with links to newly created wiki pages
Merge pull request #191 from rvraghav93/patch-1

Added Wiki pages. Updated README with links to newly created wiki pages.
Setting the clock to a uniform value of 500
This is an attempt to fix #192
BINPY SHELL: Added support for ipython notebook
`binpy notebook` will now start an ipython notebook server with all modules of BinPy loaded.
Creates a new ipynb file and initiates it with the import to load BinPy modules
Merge pull request #194 from rvraghav93/194_ipython_notebook

BINPY SHELL: Added support for ipython notebook
Fixes #195
Merge pull request #196 from rajat974/addpep8

Fixes #195
Fix in example of counters