add $default param to smartd class
add $default_options param to smartd class

+ fix a few typos in README.md
rename $default param to smartd class to $enable_default

To work around this bug in Puppet 2.7.x: https://tickets.puppetlabs.com/browse/PUP-2244
Merge pull request #21 from jhoblitt/feature/smartd_conf_default

Feature/smartd conf default