Add 2.10.4-RC2 to cross versions and travis build
Merge pull request #301 from gzm0/scala-2.10.4-RC2

Add 2.10.4-RC2 to cross versions and travis build
Fix hard-coded mangling of java.lang.Object.getClass().
Emit call graph information in .sjsinfo, for upcoming dce.

No dce is actually performed yet. This commit only emits the
necessary information.
Perform reachability analysis for dce.

The dce itself is still not actually done. The
preoptimizeJS task performs reachability analysis, from
which dce will be able to work to produce the optimized
output.
wip