Added roundto function for rounding to decimal places.
`roundto{3.14159;2}` = 3.14.
Replaced `is Vector` `is double` `is long` with `IsVector` `IsDouble` `IsLong` because I was tired of adding parentheses to the case of !IsVector.
You'd think C# would have isnt or something.
Readme now has a pic of the options menu.