Improve handling of collapsing adjacent paragraph margins
0.3.1
Expose columnHeight after ColumnFlow has run
0.3.2
Set default columnHeight before line-height is known
0.3.3
Bullet-proofing around collapsing margins logic
Update testing notes
Update README.md
Mention classList polyfill for IE9. Closes #24
Merge pull request #39 from georgecrawford/master

Small tweaks to margin collapsing