update changelog for release 0.5.12
To generate the log, run `git log --pretty='* %h - %s (%an, %ad)' TAGNAME..HEAD .` replacing TAGNAME and HEAD as appropriate.
+# 0.5.12 - Bugfix Release
+
+* d85f28c - fix: mock server matching requests with headers with multiple values (Ronald Holshausen, Tue May 5 15:23:11 2020 +1000)
+* a45d0c3 - fix: FFI mismatch json should have the actual values as UTF-8 string not bytes #64 (Ronald Holshausen, Thu Apr 30 11:16:25 2020 +1000)
+* 2003d7b - chore: roll back onig crate to 4.3.3 #64 (Ronald Holshausen, Thu Apr 30 09:50:48 2020 +1000)
+* 76250b5 - chore: correct some clippy warnings (Ronald Holshausen, Wed Apr 29 17:53:40 2020 +1000)
+* 47cc589 - chore: added clippy and fixed resulting lint errors (Ronald Holshausen, Wed Apr 29 15:32:55 2020 +1000)
+* 6f24994 - bump version to 0.5.12 (Ronald Holshausen, Fri Apr 24 10:11:33 2020 +1000)
+
# 0.5.11 - Cleaned up logging and warnings
* 3d490ef - chore: implemented Display for Interaction (Ronald Holshausen, Wed Apr 22 13:01:45 2020 +1000)
