Merge pull request #12 from ariutta/master

merge in changes from master
Merge pull request #14 from ariutta/master

merge in changes from master
Merge pull request #18 from ariutta/master

merge in changes from master
Merge pull request #19 from ariutta/master

minor updates
Merge branch 'gh-pages' of https://github.com/ariutta/svg-pan-zoom into gh-pages
change other demos to show a border