Added a -q option to suppress output if no errors, and show filename on error

I intend to use jsonlint as part of build process and would like to supress unnessecary output, so I added a -q option to make it quiet on successful validation.

Also added name of the file when error was found
Thanks for feedback. While looking at how to fix this, i realized the code path would only output usage info after stdin have been read. (this is the same in the original code).

So instead i added other options (-h, --help) to show the usage information in commit 
https://github.com/martinlindhe/jsonlint/commit/b46b0a1d41c03603e3c66e53cf03b3a96a791d5c