MB-11184: added bugsnag for capture fuller backtraces

Change-Id: I226920a4738191413602fa7699f47ed91732a1bf
Reviewed-on: http://review.couchbase.org/38144
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>