Instruct build to use JDK7.

The build had been failing due to using language level 1.7, while the
Travis runtime uses JDK6.  In this commit, we pin the Travis settings
to use the newer JDK.
Remove Jawzall in favor of plain ol' delimited.

The standard Protocol Buffer delimited writers and readers will
meet our satisfaction with Sawzall integration; thusly, we can
remove the Jawzall dependency.