Merge branch 'dev-minor' into release-v3.1.0

Also includes completed changelog entry for v3.1.0

Author: hollasch

CHANGELOG.md

@@ -1,42 +1,44 @@
 Change Log -- Ray Tracing in One Weekend
 ====================================================================================================
 
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 # v3.1.0 (2020-05-03)
 
+This minor upgrade adds some fixes and changes that are a bit more than just patches. The text now
+has subchapter headings to help readers browse content and get a bit more context. We're introducing
+new type aliases `point3` and `color` for `vec3` to better indicate the underlying mathematical
+types of parameters and variables. Overall, a bunch of small improvements that we'd recommend
+adopting, but may warrant comparison with any current projects.
+
 ### Common
-- Fix: Scattered improvements to the text
 - Fix: Include cmath in vec3.h (#501)
+- Fix: Scattered improvements to the text
 - New: Subchapters throughout all three books (#267)
 - New: Add explanation for padding `aarect` in the zero dimension (#488)
 - Change: Minor change to use new `point3` and `color` type aliases for `vec3` (#422)
 - Change: Renamed `constant_texture` to `solid_color`, add RGB constructor (#452)
+- Change: Moved `vec3::write_color()` method to utility function in `color.h` header (#502)
+- Change: Switch from `ffmin`/`ffmax` to standard `fmin`/`fmax` (#444, #491)
+- Change: Math notation to bold uppercase points, bold lowercase no-barb vectors (#412)
 - Change: Books use Markdeep's image class=pixel for rendered image fidelity (#498)
 
 ### _In One Weekend_
+- Fix: Improve image size and aspect ratio calculation to make size changes easier
+- Fix: Added `t` parameter back into `hit_record` at correct place
+- Fix: image basic vectors off by one
 - Fix: Update image and size for first PPM image
 - Fix: Update image and size for blue-to-white gradient image
 - Fix: Update image and size for simple red sphere render
 - Fix: Update image and size for sphere with normal-vector coloring
-- Fix: Improve image size and aspect ratio calculation to make size changes easier
-- Fix: Added `t` parameter back into `hit_record` at correct place
-- Fix: image basic vectors off by one
-- Change: First image size changed to 256x256
-- Change: Default image sizes changed from 200x100 to 384x216
+- Fix: Correct typo in "What's next?" list to rejoin split paragraph on "Lights." Adjust numbering
+  in rest of list.
 - Change: Define image aspect ratio up front, then image height from that and the image width
+- Change: Default image sizes changed from 200x100 to 384x216
+- Change: First image size changed to 256x256
 
 ### _The Next Week_
 - Change: Large rewrite of the `image_texture` class. Now handles image loading too. (#434)
 
 
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-# v3.0.3 (in progress)
-
-### _In One Weekend_
-- Fix: Correct typo in "What's next?" list to rejoin split paragraph on "Lights." Adjust numbering
-  in rest of list.
-
-
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 # v3.0.2 (2020-04-11)