(GH-260) Update mask docs

[pmcmaw]

There has been an oversight in the README outlining the format for mask. Currently the reference documentation and tests use integers wrapped as a string. Updating the README to be inline with all other module documentation.

puppetlabs-acl/lib/puppet/type/acl.rb

Line 203 in 1da1d13

`mask` with an integer (passed as a string) that represents the

puppetlabs-acl/spec/unit/type/acl/ace_spec.rb

Line 21 in 1da1d13

left = Puppet::Type::Acl::Ace.new('identity' => 'Administrators', 'rights' => ['full'], 'id' => sid, 'mask' => '2023422').hash

[CLAassistant]

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[pmcmaw]

fixes #260

[chelnak]

LGTM!!!