Lexicographic compare, unchecked mode

Features

• Lexicographic compare ( #29 )
• Added "unchecked" mode to expressions. After parsing, EvaluableExpresion.ChecksTypes can be set to false, which will cause all further Eval or Evaluate calls to ignore type checking, and instead panic if types are not valid. This should only be used by those who can guarantee that their types will never be invalid for the operators they're using them with. See #24 for some notes on cost/benefit.

Bugs

• Fixed bug where precedence of functions without parameters was off ( #28 )
• Fixed bug where many consecutive logical operators would evaluate out of order ( #30 )
• Fixed bug where nested ternaries would evaluate in wrong order ( #32 )

Misc

• Performance improvements when dealing with bools ( #33 )