Improve and refactor ControlParameter

- Make detector concentrate on use of parameter as a value. Using the
  result of a method call involving the parameter is considered
  legitimate use. Comparing to a value is not.
- Handle edge cases like use of if inside a condition
- Re-format specs
- Refactor smell detector
Merge pull request #309 from troessner/refactor-control-parameter

Improve and refactor ControlParameter