Add changelog entry for wire mock

Author: hlovdal

CHANGELOG.md

@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Added
 
 - Provide an `itoa` function. It is present in Arduino's runtime environment but not on most (all?) host systems because itoa is not a portable standard function.
+- Minimal Wire mocks. Will not provide support for unit testing I2C communication yet, but will allow compilation of libraries that use I2C.
 
 ### Changed