Added tests for SHNode class.
Added test case to SHNodeTests to test nodes created with convenience intializer.
Added tests for SHAction and SHBond classes.
Added one more assert to test case testing SHAction class.
Added one more test case for SHBond class.
Merge branch 'development' into unit-tests

Merged changes from development.
- Merged recent changes from development branch.
- Updated UTs because of the changes in tested classes.
Merge pull request #1 from StreamSH/unit-tests

Added unit tests for node classes.