Added *.tgz to .gitignore list.

This is to prevent and accidental commit of the file generated from npm
pack.
Added portrait resolutions to respaths.json.

Also moved and altered the entry from pull request #11.
Added more widescreen resolutions to respaths.json.

This includes the Retina 5K resolution requested in issue #12.
Added 21:9 resolutions to respaths.json.
Updated change log for 2.1.2 release.
Bumped version to 2.1.2.