chore: merge release/v1.10.0 into master

Merge pull request aws#843 from awslabs/release/v1.10.0

feat: add AWS::Serverless::LayerVersion and AWS::Serverless::Applicat…

…ion (aws#688)

chore: update README.md (aws#639)

Add link to the new AWS SAM docs.

Releasing SAM v1.6.1

chore: merge pull request aws#593 from awslabs/release/v1.7.0

Release/v1.7.0

Adding dotfiles for Travis, Flake, Coverage and Pylint (aws#359)

Merge branch 'docs' into origin-master

Policy Templates Documentation

Adding ToC to docs

Adding X-Ray Tracing support