Fix one grammar in README.
Correct the header guard style.
Minor update documentation and todo list.
Rename scram_unit_tests to scram_tests executable.
Cleanup and check performed by cppclean.
Add information about cppclean.
Introduce ProbabilityAnalysis class for quantitative analysis.

This ProbabilityAnalysis class performs what FaultTreeAnalysis class did
for probability analysis with minimal cut sets.
Add tests for ProbabilityAnalysis class.
Remove ProbOr and ProbAnd from FaultTreeAnalysis class.

This functions belong to the ProbabilityAnalysis class.
Refactor reporting probability analysis results and report number of
sets used.
fixes #55
Remove probability calculations from FaultTreeAnalysis class.
Create UncertaintyAnalysis class. Refactor functions from
FaultTreeAnalysis.
Address the strange performance bottleneck.

Direct assignment of unordered maps give worse results for probability
calculations and minimal cut set finding.
EBNF from OpenPSA MEF for MCS, Stat, and Curve reporting.
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.