Make the filter name configurable independently of the attributes

[cmlenz]

We had a case where we needed to use a custom filter, but continue to use the regular angular-gettext directive. So we need to configure the filter name independently of the attributes. This PR does that.

Projects using a custom attribute and filter will need to set the filterName option accordingly, so this is a breaking changes.

[rubenv]

Projects using a custom attribute and filter will need to set the filterName option accordingly, so this is a breaking changes.

That makes it pretty much a no-no. No breaking changes allowed anymore.

Is there any way to make this non-breaking?

[rubenv]

Also, in the interest of preventing regressions, you should never edit existing unit tests. Only add new ones. This ensures that existing code keeps working.

[cmlenz]

Oh, I didn't expect you were still reviewing the PRs here. I created it more for the record. Sorry.

If there's a chance that changes still get integrated, I would put more work into the PR to make it a non-breaking change.

[rubenv]

If it's purely additive and non-breaking, sure, why not.

[cmlenz]

I have updated the PR to make this a non-breaking change as requested.

If you don't specify the new filterName option, the extractor will continue to use options.attribute just like before. It's only when options.filterName is set that it will be used instead.

Also, I have added new tests instead of changing the existing ones.

[rubenv]

Looking good, thanks a lot!

[rubenv]

Released to NPM as v2.5.2

[cmlenz]

Thank you for the very quick release!