Update CHANGELOG

- Changes to first four renders included

Author: hollasch

CHANGELOG.md

@@ -1,6 +1,17 @@
 Change Log -- Ray Tracing in One Weekend
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+----------------------------------------------------------------------------------------------------
+# v3.1.0 (in progress)
+
+### _In One Weekend_
+- 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
+
+
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 # v3.0.1 (2020-03-31)