• Added support for the Traceur "experimental" flag to enable features like 'let' block binding, arrow functions, etc.
• Cleaned up config output to be consistent with other modules.
• Use outputFileName instead of inputFileName if it exists.  This handles the case when React's JSX compiler runs before Traceur, where Traceur should use JSX's output, not the original input file.
• Show inputFileName instead of file.name, as file.name is undefined, at least in some cases.
• Added a "return" if there was a compiler error, otherwise, the tracer.outputgeneration code will crash.
Minor reformatting of config output