`--debug` option to output requested URLs, other debug info

[phatblat]

Is your feature request related to a problem? Please describe.

Related to problems like #311 which can happen when the iTunes Search API returns unexpected JSON.

Describe the solution you'd like

I'd like a way to be able to print/dump the response JSON (and maybe HTTP headers) so that the data can be reviewed when errors occur.

Describe alternatives you've considered

Currently, the only way to view the JSON is to debug the project in Xcode or use a REST client with a problem search. Some of these issues are transient so this feature would allow mas users to easily collect this data for bug reports.

[andrewcrook]

+1

That would be useful.

[rgoldberg]

JSON (& responses in other formats, if & when mas uses such) will be available via --raw, --raw-json, and --json (see #190), or will be included in stderr error messages.

Retitled this issue to specifically be about outputting requested URLs & other debug info besides outputting response data.