Fixed expectations for the change of be_true in RSpec 3.

The conversion from test/unit for the plain assert(expression)
turned out to be tricky.
Compare

    expect(foo).to be true  # 1
    expect(foo).to be_true  # 2

1 means compare with the literal value `true`
2 used to mean "other than nil or false" but was changed to mean
  "returns true to send(:true?)". Instead, one should use
  be_truthy.

So I avoided all that by converting to more specific expectations, and
deleting one case which was IMHO meaningless and covered by a subsequent
one.

See also
http://bengribaudo.com/blog/2014/01/17/2674/rspec-be-true-be_true-are-different
changelog
rspecify tests before fixing backtraces
Test reporting the right frame for Ops.get_foo (bnc#877758).

(failing now)
Fixed to report the right frame for Ops.get_foo (bnc#877758).
Fixed method name in the warning.
Add caller info for the eval'd code.

Not actually necessary to fix the warning, because the eval'd frame is
skipped by the logger, but nicer in case we need to look at full
backtraces.
version + changelog
Ops.get - documented skip_frames
Ops.get test - improved RSpec style.
Merge pull request #124 from mvidner/ops-get

Fixed to report the right frame for Ops.get_foo (bnc#877758).