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.