Fix for incorrectly writing string values

Previously, the correct method didn't do a catch for the
:string value_type in the create method. Because of this,
it would write strings incorrectly initially as arrays,
and then take a second run to correct them. This commit
changes that by correctly unwrapping the string value
in the create method.
Remove unnecessary comments
Ignore the vendor directory
Merge branch 'master' of https://github.com/glarizza/puppet-property_list_key
Handle Hash values correctly in value= method

Previously, the value= method would treat :hash value
types like arrays and write the entire hash-wrapped-in-an-array
directly to the file. This was incorrect, as the hash
comes in as the first element of the array. Incidentally,
the create method worked just fine.