Add initial event tree example file.
Refactor Analysis functions in the Probability and Uncertainty analysis.
Refactor Probability reporting.
Refactor main function in scram.cc.
Refactor CheckGate member function of RiskAnalysis.
Refactor XOR gate expansion function in FaultTreeAnalysis.
Refactor Atleast gate expansion into a separate function.
Rename VOTE gate to ATLEAST.
closes #59
Merge INHIBIT and AND gate expansions.
Refactor gate expansion saving and retrieval.
Add tests for the MCUB and Rare event calls from command line.
Refactor gate children to vector with indices algorithm in
FaultTreeAnalysis.
Switch to Flat Sets. Performance optimization for probability calculations.

Overall optimization must be from 2 to 5 times depending on the
analysis.
Record new performance times for performance tests.
Refactor Superset class.
Refactor the use of indexed mcs in FaultTreeAnalysis.
Remove negative event failure contribution reporting.
Refactor positive and negative gate expansions.
Add a test for negative unknown gate.
Print parameters of distributions for test results.