addresses issue 216

Successfully tested against a locally installed MongoDB 2.6.5. Please
test and review.

Don't merge / release before all known MongoDB servers are updated to
a version >= 2.4
Merge branch 'fix/issue216' of github.com:radical-cybertools/radical.pilot into fix/issue216
resolve conflicts from merge from devel
Merge branch 'devel' of github.com:radical-cybertools/radical.pilot into devel