Add Catmandu::Fix::oops

[nichtich]

This fix throws an error with error messages passed as string and/or read from error field such as set with validators. An example is given in the SYNOPSIS. I'd further like to make this functionality more easily available via command line as discussed in #274.

[coveralls]

Coverage increased (+0.02%) to 94.518% when pulling aa8375c on oops into e55ec00 on dev.

[phochste]

What is the difference with Catmandu::Fix::error?

[nichtich]

Catmandu::Fix::error results in a verbose error message to STDOUT such as:

$ catmandu convert Null to Null -fix 'error("messsage")'
Oops! One of your fixes threw an error...
Error: message at /home/voj/proj/Catmandu/lib/Catmandu/Fix/error.pm line 17.
Input:
$VAR1 = {};

Catmandu::Fix::oops only emits the actual error message to STDERR:

$ catmandu convert Null to Null -fix 'oops("messsage")'
message

Moreover the message does not need to be a fixed string but can be read from a field (see SYNOPSIS).

I would also be fine with replacing the current Catmandu::Fix::error with Catmandu::Fix::oops - this would slightly change existing behaviour of the error fix and extend its functionality.

[nics]

A switch to make errors concise and syntax to get a value from a path are so useful I would like to implement them Catmandu wide. The first is trivial to implement.
The feature/data_path branch could implement the second quickly. The feature/path branch makes it easy to integrate these path related features more cleanly though.

[nichtich]

This has already been solved.