bump version to v0.4.5

fix sketchtool command line to work with Sketch v48

rename images to only allow safe characters

fix for mac os high sierra

add objectID to image to make it unique

add google analytics, change some wording

separate schema and assets upload

bump to version 0.3.1, remove buggy icons in dialog, rename to appche…

…f, and only upload images in 2x size.

update version number and readme

Merge pull request #1 from adamkirkwood/patch-1

Add compatibleVersion and version badges