v0.4.0, 19.05.14 -- Make only cells with conflicting names unique during saving.
This change effects the API of the Layout.save() call.
-- Use numpy for conversion to GDS internal coordinates while saving
-- Fixed Elements constructor for 1-element lists
-- Track references to Elements and CellReferences separately
-- Cache bounding box property
-- Removed .uniquify_names methods. Uniqification is applied
if and only if the name has a duplicate