Upgrade AWS provider and remove now-redundant second apply

[austinbyers]

to: @javuto cc: @airbnb/binaryalert-maintainers size: small

Background

As of AWS provider v1.10, Lambda functions with auto-publish correctly recompute the function versions, obviating the need for our second terraform apply during a deploy

Changes

• Upgrade AWS provider minimum version to v.11.0 (the latest release)
• Remove second terraform apply (a single one works now)
• Remove terraform validate - validation automatically happens during apply

Testing

• Unit tests verify functionality of CLI
• We have other Lambda projects with the new AWS provider which deploy as expected

[coveralls]

Coverage decreased (-0.02%) to 93.115% when pulling 65cedde4697411a97da70db1a6db8c44f939c690 on austin-update-provider into 2f0ee271e266e220a278a1000162febc8c38d7ba on master.