Require ruby 2+

ref  #1836
Merge pull request #1837 from seuros/master

Require ruby 2+
raise error if ruby 1.9.3 is detected.
allow user to specify max size of error messages

Errors can have messages that are very large. When they are raised,
redis space is rapidly depleted.

An example of this problem is an INSERT or UPDATE in ActiveRecord
with a very large blob of data. When ActiveRecord fails, it puts
the entire SQL statement into the error message.
Merge pull request #1843 from covermymeds/truncate-huge-error-messages

Allow user-specified maximum error message size
Truncate error message to 10k, #1843
Remove librelist, add ggroup and SO tag
Move copyright to contribsys
Fix race condition in retry_all, fixes #1851
Note about assignment rights
Merge pull request #1838 from seuros/fail_on_ruby1_9

Raise error if ruby 1.9.3 is detected.
Send info cmd to redis directly, fixes #1865
Sidekiq does not exit on USR1, so we shouldn't need to tell Upstart about it
[WEB UI] Add Kill button to retriable jobs, closes #1866
rdoc
Merge pull request #1867 from seuros/killswitch

[WEB UI] Add Kill button to retriable jobs
changes
fixup to poll_interval logic, so calling poll_interval= has expected behavior
Merge pull request #1874 from rocketmobile/master

Calling `poll_interval=` doesn't account for scaling due to interval randomization
[Webui] Add back button