Remove bootclasspath hacks (#138)

* As we no longer support Java 7, we don't need to change the
bootclasspath.

* Remove assert that is inconsistent with the documentation.
This wasn't triggered before, because classes on the bootclasspath don't
have assertions enabled.

* Fix javadoc error. Errors in javadoc are now failures.

* No longer test on JDK 7.
15 files changed