Add support for the `vips_gamma()` function via a new func `Gamma()` …

…on `ImageRef` (davidbyttow#433)

* Add support for vips_gamma() function for adjusting the gamma of the image

* Add support for vips_gamma() function for adjusting the gamma of the image

* Fix test for gamma

Update DevOps (davidbyttow#409)

* update dockerfiles

* drop macos test automation

* clean up ci

* Update New golden images

* Fix dockerfile

* Update golden images

regenerate images (davidbyttow#357)

Sanitize vips version string (davidbyttow#354)

fix dpi param for svg and pdf davidbyttow#203 (davidbyttow#268)

Animated GIF support (davidbyttow#246)

* - add golden

* - load animated GIF
- export GIF
- resize animated images
- export animated images

* - add Pages to ImageMetadata
- when building ImageMetadata add all the props

* - Support rotation of animated images
- Add imageRef.Grid() func
- rename ...pages... functions to something more reasonable

* - add golden

* - keep frame (page) order when rotating 270

* - Return error for unsupported operations on multi-page images
- fix 270 rotation of multi-page images
- Pages() instead of GetPages() is more Go like
- Orientation() instead of GetOrientation() is more Go like

Add Transform ICC Profile API (davidbyttow#208)

* Add TransformICCProfile method

* Add tests for transform ICC profile method

* Fix transform ICC case for images without ICC profile

Merge pull request davidbyttow#231 from wix-incubator/optimize-icc-16…

…bit-fix

Fix OptimizeICCProfile for 16-bit images

Fix go reportcard

Update unit tests