DLTK 5.6 (Neon.1)

Modernize o.e.dltk.ruby.core.tests a bit.

* Don't call deprecated codeComplete method, use the new one with
timeout instead.
* Convert AllTests to JUnit 4 style suite.
* Removed not needed Requires from manifest.
* ZipException is an IOException so no need to catch it specifically if
no special treatment.

Change-Id: I34ab76df0b4f9768991955b3046372cd8b9f9e81
Signed-off-by: Alexander Kurtakov <akurtako@redhat.com>