doc(CHANGELOG): Update changelog for release 4.2

Author: gfieni

CHANGELOG.md

@@ -1,5 +1,25 @@
 # Change Log
 
+## [4.2](https://github.com/Spirals-Team/powerapi/tree/4.2) (2017-11-02)
+[Full Changelog](https://github.com/Spirals-Team/powerapi/compare/4.0...4.2)
+
+**Implemented enhancements:**
+
+- Update projects and libraries to Scala version 2.12
+- Implement a disk module (only for Linux)
+- Use an asynchronous API for InfluxDB
+- Use the cgroup statistics to retrieve the cpu usage of a docker container
+- Improving the resilience of power conversions
+
+**Fixed bugs:**
+
+- Bluecove libraries download URL for sbt
+- Travis CI build: JDK version 7 to 8, Ruby installation, build failing on pull-request
+
+**Closed issues:**
+
+- Version mismatch [\#87](https://github.com/Spirals-Team/powerapi/issues/87)
+
 ## [4.0](https://github.com/Spirals-Team/powerapi/tree/4.0) (2016-04-14)
 [Full Changelog](https://github.com/Spirals-Team/powerapi/compare/3.4...4.0)
 
@@ -120,5 +140,4 @@
 - Bug \#19 [\#20](https://github.com/Spirals-Team/powerapi/pull/20) ([mcolmant](https://github.com/mcolmant))
 
 
-
-\* *This Change Log was automatically generated by [github_changelog_generator](https://github.com/skywinder/Github-Changelog-Generator)*
+\* *This Change Log was automatically generated by [github_changelog_generator](https://github.com/skywinder/Github-Changelog-Generator)*