Report file uploads to IRC

[Aketzu]

This handles file_share message subtype which is sent when e.g. screenshot is pasted to Slack channel. It shows both Slack-internal link and public link. For the public link to work Slack config "Enable public file URL creation" must be enabled and file uploader must also click "Create external link" on the file.

Looks like this in IRC channel

20:58 < slack> <aketzu> File uploaded 
             https://team.slack.com/files/aketzu/F60UD9R2L/pasted_image_at_2017_04_18_08_57_pm.png / 
             https://slack-files.com/T0LK1LT6W-F60UD9R2L-8fb1c182e4 - comment here

Fixes #22

[coveralls]

Coverage decreased (-1.6%) to 97.861% when pulling 2d8ee52 on Aketzu:master into 28dd48b on ekmartin:master.

[ekmartin]

Thanks! Would you mind adding a test or two as well? Could probably look quite similar to this: https://github.com/ekmartin/slack-irc/blob/master/test/bot.test.js#L241-L252

[ekmartin]

Isn't showing one of these enough? I.e. message.file.permalink_public || message.file.permalink.

[Aketzu]

permalink_public is always generated even if file is not shared. So it's rather hard to guess which would be better to show.

[Aketzu]

permalink_public doesn't seem to work for logged in users before it is "created". On external link creation Slack seems to send file_change event but not file_public event. Additionally file_change has just file id without any other details and slack.rtm.dataStore doesn't seem to have method for looking up file by ID. So this would need some own temporary storage for storing file id + url, then on file_change event poll URL whether it works and finally generate another line to IRC if it succeeds.

So I'd guess showing both links is somewhat reasonable.

I also added tests.

[coveralls]

Coverage increased (+0.009%) to 99.465% when pulling 7440faf on Aketzu:master into 28dd48b on ekmartin:master.

[ekmartin]

Sorry about the slow response. This is now published in version 3.10.0 - thank you!