Fix pretty printing for fragmented spans.

Upgrade Fragment to contain pen position.

Clean up ParagraphConstruction.

Use infix operators for constructing test data.

Implement "plain" interface.

Create "plain" interface.

Add module for working with rectangle coordinates.

Add explicit scale to test font.

Automatically discover test specs.

Separate tests by module.

Add unit tests for spanToRuns.

WIP version with WIP interface.