Allow custom install location

Changes to allow a custom installation path other than the hard-coded /opt, and created a symlink that is unversioned.

class { "play": version => "2.1.0", install_path => "/opt/tools" }

should then create;

/opt/tools/play-2.1.0
and a symlink
/opt/tools/play -> /opt/tools/play-2.1.0