[travis-ci] test with MRI 2.1.0 + JDK 7 as well as 8 for JRuby
avoid the VERSION constant already initialized warning (with bundle exec)
refactor our synchronized delegator to work with MRI/JRuby 1.8 std-lib

this due delegator.rb library doing eval on `initialize` - thus `method_missing` is not actually called for __send__ delegation to the target. we avoid this by unpatching the work done by MRI as well as JRuby in 1.8 mode (which is slightly different since it tries to pre-generate a module that it includes based on target's class do not do that much eval).

changed tests due a bug in delegator.rb that affects 1.8 - we've been expecting a delegated Array#each (with a block) which won't work since the block is not passed to the target ...