JPEG output: enable progressive compression

I made a corresponding update in canvas that has now been merged:
https://github.com/LearnBoost/node-canvas/commit/d72c1bbf022b0c56e242211f25c584c4eb6a4e6b

Progressive JPEGs are smaller (2-7%) and have a lower time-to-first
paint in browsers.
Merge jpeg-progressive-option (#22) into ifixit-production

JPEG output: enable progressive compression

I made a corresponding update in canvas that has now been merged:
https://github.com/LearnBoost/node-canvas/commit/d72c1bbf022b0c56e242211f25c584c4eb6a4e6b

Progressive JPEGs are smaller (2-7%) and have a lower time-to-first
paint in browsers.