Add setup script to easily generate make files, make them and install in OSX
Add [NumberIsFloat] attribute for PlayScript

This class level attribute instructs the compiler to use single
precision floats instead of doubles for the PlayScript Number type. It
is applied recursively to all Number types in the class.
Add PlayScript implicit conversion from double to float
Add null checks to each visitor Accept function
Add PlayScript implicit conversion from float to int/uint

Previously all Number types in PlayScript were doubles; but with the
addition of the [NumberIsFloat] attribute, Numbers can be floats, and
the conversions are required.
Fix typo in NumberIsFloatAttribute.cs
Fix typo in class.cs
Fix mcs tests

Using Convert.ToString for string constants wasn't generating the exact
same IL as a cast to string for null constants. The Convert.ToString
change was only made for consistency with the numeric types, but is not
required.
Support constructors for PlayScript scalar classes

This isn't true constructor support, instead it converts expressions
like:

	var num:Number = new Number(1.0);

to:

	var num:Number = 1.0;

This resolves issue #140.