Remove travis runs for perl versions 5.12, 5.14 and 5.18
Remove travis runs for perl versions 5.12, 5.14 and 5.18

Tests on versions 5.10 and 5.20 should suffice.
As each test is longer than 20 minutes reduces the build time by an hour.

iimog/bcgTree,iimog/bcgTree,iimog/bcgTree,iimog/bcgTree,iimog/bcgTree