Converted the implementation of connections from list to dict
Added PowerSource() and Ground() classes with documentation.
Added an example of using PowerSource() and Ground()
Added tests for PowerSource and Ground
Corrected a few bugs
Merge branch 'develop' of https://github.com/BinPy/BinPy into sources
Merge branch 'develop' of https://github.com/BinPy/BinPy into sources
Merge pull request #101 from SSR09/sources

Implemented PowerSource() and Ground() with tests and Examples