Renamed file to files (avoid py conflicts)
Duplicate of PR #3585 (by @minrk)
Since it hasn't merged yet...
Missing notebook_name param (mergetool error)
Typo - fliter -> filter
Added TODO comment
Moved _transformer dict init before reg transformers to avoid name error
Why export text?  Removed.
Should be referenced from the templates directly.  No need to export.
Extension map repalced with ConvertFigureTransformer
Forgot to remove it from the def. config.
Forgot to replace cell_transform with transform_cell
Removed a lot of blank lines
YAML -> Config mapping working.
Rename: Template -> Format
Typo, extension->out_type
Import fix file->files
Repalce destination->build_directory.  "None" test by bool cast...
Typo, FileWriter->FilesWriter
Make sure the destination directory exist!
Removed extra blank
Typo, again, FileWriter->FilesWriter
Removed TODO.