subclass importer from Sketchup::Importer
use Sketchup::Importer constants
add PREF_KEY constant to exporter
added @options variable
added persistent option stl_format
exporter persistent options
cleanup
Merge pull request #66 from jimfoltz/subclass-importer

Subclass importer - fix issue #62
Merge pull request #67 from jimfoltz/exporter-save-settings

Persistent options for Exporter. I'm adding an issue that we need to add a "Model Units" option to the exporter.
Bumped version number to 2.0.0.
Merge pull request #72 from thomthom/master

Bumped version number to 2.0.0
Added  Dutch translation. Thanks to Jan "brewsky"
Merge pull request #74 from thomthom/master

Added Dutch translation. Thanks to Jan "brewsky"
Updated README to link to Extension Warehouse for RBZ instead of repo.
Delete sketchup-stl-1.0.0.rbz
Fixed a bug in heal_geometry where edges where added instead of healing. Fixes #77
Merge pull request #78 from thomthom/master

Fixed a bug in heal_geometry where edges where added instead of healing. Fixes #77
using ours