URL percent escape for unicode characters in filepath
fixes #90 (rendition metadata)
Media Overlays bugfix for EPUBs that do not use a OEBPS or EPUB (or whatever) "root" content folder: the ReadiumSDK is slightly odd in that it returns absolute paths with prefix '/' (instead of say: "OEBPS/html/chapter1.xhtml", it returns "/html/chapter1.xhtml")
Merge commit '4ad3e73e5e2034f05d66e783c98f643d33f4bfb1' into develop:

  Media Overlays bugfix for EPUBs that do not use a OEBPS or EPUB (or whatever) "root" content folder: the ReadiumSDK is slightly odd in that it returns absolute paths with prefix '/' (instead of say: "OEBPS/html/chapter1.xhtml", it returns "/html/chapter1.xhtml")
  fixes #90 (rendition metadata)
  URL percent escape for unicode characters in filepath