Bump version to 2.9.0

Fix typo in pom.xml

Bump to v2.5.0

Merge branch 'master' of github.com:spencerwi/Either.java

Add flatMap, add javadocs, refactor some tests, bump to 2.3.0

Move to maven instead of gradle

Bump version to 2.2.0 and update changelog

Fix signing/publishing with gradle

Bump version number in README.md