Update ruby-mime-types to 1.19.

== 1.19 / 2012-06-20
* New MIME Types:
  * XCF Gnome Images (image/x-xcf, image/x-compressed-xcf;
    .xcf). https://github.com/halostatue/mime-types/issue/17
  * Types reported in https://github.com/halostatue/mime-types/issues/12:
    * DV (video/x-dv; .dv)
    * IVF (video/x-ivf; .ivf)
    * Matroska (video/x-matroska; .mkv)
    * Motion JPEG (video/x-motion-jpeg; .mjpg)
    * RealMedia (official; application/vnd.rn-realmedia; .rm)
* New extensions:
  * dcm (application/dicom); https://github.com/halostatue/mime-types/issue/16.
  * Types reported in https://github.com/halostatue/mime-types/issues/12:
    * 3g2, 3gpp2 (video/3gpp2)
    * mpeg (video/mpeg)
    * mxf (application/mxf)
    * ts (video/MP2T)
    * ogg (video/ogg)
* Fixed MIME Types:
  * Adobe AIR application installer packages was missing a
    hyphen. https://github.com/halostatue/mime-types/issue/13
  * Types reported in https://github.com/halostatue/mime-types/issues/12:
    * audio/x-pn-realaudio extension is .ra, not .rm.
* Resolved https://github.com/halostatue/mime-types/issues/8. Apparently some
  people run the tests on Linux. Imagine that.

(taca)