Fix error from instance.tags[key] returning nil
Merge pull request #20 from cheald/master

Use AWS.memoize
update CHANGELOG, bump release
add version badge to README
Merge pull request #19 from tomconroy/feature-patch-tags

Fix error from instance.tags[key] returning nil
update changelog, bump version
Add instance_status_ok? method to filter servers
Add configuration switch to filter by status_ok?
Merge pull request #23 from tomconroy/feature-status-ok

Add `instance_status_ok?` method to fix problem connecting to unavailable instances
Update changelog and docs, bump version for release
Disable colorized output from StatusTable unless STDOUT.tty? is true.
Merge pull request #27 from Futurelearn/master

Disable colorized output from StatusTable unless STDOUT.tty? is true.
Update changelog for 0.0.16
Bump for 0.0.16
Allow for specifically mapping which role should map to an EC2 tag