Updated README.md to reflect the change from version 4.2.1 to 4.2.1.
Updated README.md to reflect the change from version 4.2.1 to 4.2.1.

appliedtopology/javaplex,appliedtopology/javaplex,appliedtopology/javaplex,appliedtopology/javaplex,appliedtopology/javaplex,appliedtopology/javaplex