Conversion + cleanups in o.e.dltk.ruby.formatter.tests.

* Convert AllTests to JUnit 4 style suite.
* Formatting fixes.
* vararg usage.
* Single Charset constant in the activator instead of having it in
multiple places.
* Drop unneeded dep from manifest.

Change-Id: I4517b655ef008f3ec7877938f2dfaba8a1075003
Signed-off-by: Alexander Kurtakov <akurtako@redhat.com>