Enable MongoDB build on TravisCI [DATAMONGO-1411]

[spring-projects-issues]

Mark Paluch opened DATAMONGO-1411 and commented

Travis CI still runs MongoDB 2.4.2. We require MongoDB 3.2. Build also fails due to missing/release-promoted driver snapshot versions

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Referenced from: pull request #358, and commits 8d96f62, 2acc373, f5cfcda, 42fad62, c8fe02e

Backported to: 1.9.2 (Hopper SR2)