Enhancement: Interactive forest plot

[badgettrg]

See working example at http://openmetaanalysis.github.io/Epidural-corticosteroids-for-spinal-stenosis/interactive-forest-plot.html

[badgettrg]

In response to suggestion by @timelyportfolio, http://www.htmlwidgets.org/ seems a very good method. I have mixed js and svg at https://openmetaanalysis.ocpu.io/home/www/editor-dx.html (not fully implemented, be patient when you hover over a study name). Full JS implementation could be similar to http://www.simile-widgets.org/ .