Minor (minor minor) grammar fix in README.md and correction on needed Maven version.

The Maven plugin 'org.apache.maven.plugins:maven-shade-plugin' requires Maven 3, breaking compatibility with Maven 2

Signed-off-by: Mloc-Argent <colmohici@gmail.com>
Merge pull request #415 from Mloc/readmefix

Minor (minor minor) grammar fix in README.md and correction on needed Maven version.