Better SVG support (#2614) ...

* Better SVG support

* Images are loaded using canvas which enables pre-scaled textures
* Scaling is done by providing an extra parameter `sourceScale` to the `fromImage` method
* Size of the original SVG source is checked with an extra XHR (necessary step for the canvas API to work)
* Supports data URI based SVG

* Fixed brace-style.

* Added util tests.

* Rebased to latest dev. Added 'px' support.

Prefer const (#3002) ...

* added prefer-const rule to .eslintrc

* eslint const autofixes

* manual let to const changes; lint free;

* added brace style 'allman' to eslintrc

* brace style, comment fixes and default arg

* brace style fixes

* more brace styles

* Point default args

* Point brace styles

* Observable Point default args

* more brace styles

* jsdoc comment style

* brace style

* brace styles and small jsdoc fix

* brace styles

* removed unneeded eslint inline comment

* brace styles; lint free

Replaces Testem with Floss (#2775) ...

* Updates tests to use Floss/Electron

* Adds testing after building

* Don't run test twice