Always update snapshots on CircleCI builds
Always update snapshots on CircleCI builds

We had some issues building the current development version on CircleCI.
As it turned out, Maven did not use the latest snapshots of some
dependencies, but our code depended on these new versions. This commit
adds the `-U` switch to the 'dependencies' phase of CircleCI, so that
snapshots will always be updated, and also enables downloading of the
plugins, so that they will be cached too.

Fixes #164

osiam/connector4java