Upgrade AWS version to 1.8.5 which has support for AWS STS and includes
support for reading 'aws_session_token' in ProfilesConfigFileParser,
which is used by ProfilesConfigFile in the ProfileCredentialsProvider.
The ProfileCredentialsProvider is also included in the
DefaultAWSCredentialsProvider in this version of the SDK - making the
code portable between all of our environments; including dev since
everything else also looks for credentials in ~/.aws/credentials and not
~/.aws/config.