testPutBadETag is sending an ETag header

I think the right header to send the etag value should be If-Match.
Merge pull request #55 from fserena/patch-3

testPutBadETag is sending an ETag header
remove duplicate testAcceptNonRdfPost

Remove unimplemented method testAcceptNonRdfPost() from
CommonContainerTest as it's already being tested in
NonRdfSourceTest.