Merge pull request #119 from flyinva/master

French translation file
Added french from #119 #72
Updated sortable to support scrolling of the viewport

jquery UI was removed as a dependency so "sortable" had to be
re-implemented.

Turns out that that isn't so straightforward once you get issues
such as scrolling, first & last elements, 2-dimensional sorting
and what not involved.

The current implementation of "sortable" requires the
scrollParent (if one exists) to be passed in
so it can determine the viewport offsets.
Correctly maps the overview scale to the impressjs scaling

This bug was introduced when the feature was added
for the overview mode to resize slides as users
changed their scale.

The problem was that the default (non-scaled) size of a slide was reduced
by half but the impressjs generator wasn't updated
to reflect that fact.

Fixes #122
Export stubs
Bespoke skeleton
Defaults to english if it can't find a translation #72
Removed blank template file
Added JSON export capability
Implemented import
Switched from keymaster to mousetrap
Exports JSON in a pretty-printed format so it can be versioned

Fixes GH-123
Fixed issue where canvases leaked every time modes changed!
Fixed a bug introduced by invoking remove on destroy events
Tweaked the positioning of the Y rotate control
Abstracted away the mousetrap dependency
Doesn't dispose the models when leaving transition editor
Moved sortable to interactions package
Sorting slides actually sorts the slides again.
No longer highlights stuff when dragging elements