Travis CI fixes. Run all Unit Tests first, THEN assemble DSpace +
Mirage2
Move assembly of 'dspace-installer' into a default profile so that it
can be disabled as needed for TravisCI
Default to giving Unit Tests 512MB of memory. Provide a -Dsurefire.argLine
option to pass a different setting to m-surefire-p.
Merge pull request #648 from tdonohue/travis_fixes

More Travis CI build fixes related to DS-2133