lib-gwt-svg 0.5.15 released to address dropped SVG1.1 features in Firefox 59+)

I am releasing a new version of lib-gwt-svg to preserve compatibility with Firefox 59+. After Chrome 48+, Firefox has begun dropping compatibility with SVG1.1 features (to prepare for SVG2.0 I guess ?). Luckily for us SVG1.1 users, Philip Rogers has updated his polyfill to address just that. Restoring compatibility was just a matter of upgrading the polyfill, which is the only new (though crucial) feature of this release.