Update CHANGELOG.md
Release: version 2.4.0
Release: version 3.0.0
Release: version 3.1.0
Release: version 3.2.0
updating license links
Release: version 3.2.1
Update Changelog

Fix Bold Formatting in latest entry.
Merged 3.2.1
Merge branch 'master' of https://github.com/mopub/mopub-android-sdk

Conflicts:
	mopub-sdk/build.gradle
	mopub-sdk/pom.xml
	mopub-sdk/project.properties