Add Anchor pattern to client.pp

The class mysql::client::install is "contained" in the mysql::client to avoid floating.
Update the Anchor pattern workaround

Add a step to the anchor pattern and add comment to clarify the need of this workaround.
Ref : http://docs.puppetlabs.com/puppet/2.7/reference/lang_containment.html#known-issues
Ignore the coverage directory
Fix raise_error deprecation warning
Merge pull request #350 from Element84/IgnoreCoverageDir

Running rake spec creates a coverage directory that should be ignored.
Merge pull request #349 from Element84/SpecDeprecationWarning

Deprecation warning when running rake:spec
Merge pull request #343 from Bit-Doctor/patch-1

Add Anchor pattern to client.pp