First stab at porting Test::Reporter functionality from cpantimes to cpanminus

A couple of issues that probably need input from @miyagawa before merge...

* Currently if everything is in place (Test::Reporter, etc installed; and a metabase profile has been configured) it defaults to sending reports. Should there be an explicit opt-in, rather than an opt-out?
* It doesn't output any mention of the reports to STDOUT. This is because the reports are sent between outputting `Building and testing $dist ...` and outputting `OK`, so there's nowhere good to output it. I can play around with this, but it may require splitting the `Building and testing` line into two lines.