fixed install_from attibute
Merge pull request #7 from llonchj/fix_dovector

fixed typos
fixed recipe description
Merge pull request #8 from llonchj/from_package

`from_package` recipe
kitchen.cloud.yml: some images updated
Added integration tests for imap protocol
Package installation and template generation logic standardized using a Dovecot::Conf#require? method (fixes #9)
README: some minor improvements