Update CHANGES.md

Update in preparation for release 3.1.2

Author: RosalynHatcher

CHANGES.md

@@ -3,6 +3,16 @@
 See https://github.com/cedadev/cf-checker/milestones?state=closed for full details of each release.
 
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+## July 2019
+
+CF Checker release 3.1.2
+
+This is a bug fix release
+
+[#64](https://github.com/cedadev/cf-checker/issues/64): Required version of cfunits is v1.8 to v1.9.1
+
+[#65](https://github.com/cedadev/cf-checker/issues/65): Checker not giving a warning when variable is type int and scale_factor/add_offset are float
+
 ## April 2019
 
 CF Checker release 3.1.1