GH-135 Allow passing of DOT meta attributes

Allow passing additional DOT attributes (for disabling splines etc.).

Fixes GH-135-Pass_DOT_Attrs

Signed-off-by: Gordon Smith <gordon.smith@lexisnexis.com>
Merge pull request #143 from GordonSmith/GH-135-Pass_DOT_Attrs

GH-135 Allow passing of DOT meta attributes

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>