The logical functions needed to be able to handle an evaluation returning nil.  Fixes issue #43.
Exploring parsing strings as variables.

@"\"Foo\" + \"Bar\"" would be equivalent to @"$Foo + $Bar"
@"'Foo' + 'Bar'" would be equivalent to @"$Foo + $Bar"
Numbers can now be entered as hex, beginning with either "0x" or "0X".

This does not interfere with the multiplication operator, because "x" is not recognized as multiplication; "*" and "×" (the actual unicode multiplication sign) are.
merging in remote changes
Adding more NSDecimal functions
Updated project settings.
Converting to modern literal syntax
Clean up the implementation of random().  Fixes #34.
Implement some more high-precision trig functions
What could be more worthwhile than rewriting comments?
Use new high-precision functions
Function resolution should pass variables through
Modernize ARCHS setting
Exploring parsing strings as variables.

@"\"Foo\" + \"Bar\"" would be equivalent to @"$Foo + $Bar"
Pruning unused methods from the tokenizer
Reparenting DDMathStringTokenizer
Renaming methods to conform to what NSEnumerator declares
Moving ivars to inside @implementation blocks
Modernizing some syntax
The future is ARC.