textproc/py-transifex-client: Update to 0.11

• Update PORTVERSION and distinfo checksum (0.11)
• Enable builds for Python 3.x
• Enable "concurrent" Python installation
• Add RUN_DEPENDS (urllib3)
• Switch to CHEESESHOP for MASTER_SITES
• Enable NO_ARCH (architecture independent)
• Add LICENSE_FILE
• Update test target
• Strip pkg-descr WWW: URL trailing slash