Update readme.md
Merge pull request #21 from bhardin/patch-1

Update readme.md
Add the ability to pass an array of health checks to the rolling deployment.
Improve error output when using ec2:status and ec2:ssh.
Fix additional newline issue in output of rolling deployment.
Update Readme and Changelog for 1.4.2.pre4.
Prepare for v1.4.2.pre4 release.
Allow the expected result for the healthcheck to be specified as a regex or an array - see readme.md for more detail
Update readme
Update readme
Fix deployment by uncommenting the call to 'top.deploy.default'.
Updated change log and version for v1.4.3.pre5 release.
Updated read me to point at correct pre-release version.
Fixed an issue with healthcheck expected response output.
Update changelog and version for v1.4.3.pre6 release.
Updated readme to point to correct pre-release version.
Set HTTP open timeout to 5 seconds to prevent hanging for the entire default timeout waiting for the server to respond.
Revert "Set HTTP open timeout to 5 seconds to prevent hanging for the entire default timeout waiting for the server to respond."

This reverts commit 5e4eb25e43c209b4c4dc84603a03315d5a459ddc.
Pull AWS credentials from ENV if available

Use AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY environment variables
for AWS credentials if they are not present in the ec2.yml config.
Exit 1 when encountering rolling deployment errors, after displaying the rolling deployment status overview.