Added configuration option to disable autoconfiguration

[Cawllec]

This adds two functions, load_integrations & load_integration(integration) that allow Bugsnag integrations to be loaded during runtime.

By default, load_integrations will be run when the bugsnag module is required. This behaviour can be disabled using the environment variable BUGSNAG_DISABLE_AUTOCONFIGURE.

Tentatively fixes #391, #403

[snmaynard]

What manual testing has been done?

[Cawllec]

I've tested it in rails to ensure the environment variable stops it from loading the railtie, which works correctly. I guess the main issue would be that it still loads in bugsnag\integrations\rack regardless of environment variables as it's always done that separately to the other integrations.

Edit: Meant bugsnag\integrations\rack, not rake.

[snmaynard]

We should test it for all the integrations to ensure that manually loading the sidekiq integration (as an example) works and we dont need to make any changes to support the later loading.

[Cawllec]

Now tested and confirmed to work with:

• Sidekiq
• Rails
• Resque
• Rake

Does not work with:

• Rack

[kattrali]

Rack or rake? Checking because rake was mentioned in #419 (comment)

[Cawllec]

Rack. We loaded the Rack integration outside of the load_integrations loop previously, probably means removing it from there would make this a breaking change.

[kattrali]

What broke when moving the import to the load_integrations loop?

[Cawllec]

Nothing I suppose. I haven't added it to the loop yet (as it was separate anyway), but it shouldn't change the expected behaviour if I do. I'll do that and test it.

[Cawllec]

Everything works as expected with rack, and there's no magic conf happening.