Fix some issues related to linear.
fix SymmetryCube name clash
Include CmdLine modules in builds.  Adjust image examples for SVG.
Fix breakage from Diagram type change.
Add dummy cabal file to appease travis
Add force-layout to head deps for travis
Fix for Diagram type change that I missed
Merge pull request #69 from diagrams/wip-linear-fix

Update for linear and new Diagram type. 
I think it's best to merge and make separate branches
for further fixes.

Nice work Ryan !