Added scalarNode to support timeout parameter in configurationfile

forgot to add it to the Configuration class.
Also add timeout config param to MZPostmarkExtension class
Merge pull request #17 from wrep/feature/attachment-improvements

Some attachment improvements and change to curl timeout.
Support for batch sending
Updated readme with batch example
Merge pull request #18 from ruudk/feature-batch

Support for batch sending
Merge branch 'refs/heads/master' into feature/fosuser-mailer