Add build status

Add coverall badges

100% line of code coverage

Improve code coverage for iterative parsing

Assert on impossible state transition in Transit(); Put the last case and all non-enumerated cases(also supply assertion for them) in  for code coverage.

Use assertion for impossible case(The Predict() can ensure the token is ColonToken, otherwise it would be marked as Error state. So there is no need to check ColonToken again).

Remove deprecated FileStream