CI: Install Gradle 2.10
CI: Install Gradle 2.10

We need a newer Gradle version to run checkstyle. Also makes CI more
stable as we don't depend on what version Travis is currently using.

danilovesky/workcraft,jrbeaumont/workcraft,tuura/workcraft,tuura/workcraft,danilovesky/workcraft,danilovesky/workcraft,workcraft/workcraft,danilovesky/workcraft,workcraft/workcraft,tuura/workcraft,workcraft/workcraft,jrbeaumont/workcraft,workcraft/workcraft,jrbeaumont/workcraft