Be able to provide a different secrets_dir, solves #4

@nasali would like to use a different secrets_dir.  While his pull was
workable, there are situations where the same type of configuration was
possible but it was done solely through the eb.yml instead of an
additional environment variable.  This change provides a new
‘secrets_dir’ key under the root node.
Pass through new additional options to eb_deployer

:package_bucket, :keep_latest: :version_prefix

Solves #5
readme formatting
Bumping version to 1.0.0.  Been stable and deploying via continuous delivery for several months.
Merge branch 'master' of https://github.com/alienfast/elastic-beanstalk

Updating to from original branch to stay in sync