More DRY tests

[emiln]

Currently the behavior tests are a horrible exhibit of repeated boiler plate code. It would be nice to express facts in a manner like:

(succeeds "Fact string for Midje" "tip-source-filename")

and

(fails "Fact string for Midje" "tip-source-filename")

I think refactoring would provide much cleaner test code.

[emiln]

Elaborating slight on the idea, it should also be possible to state the following:

(succeeds "Fact string."
  "filename-1"
  "filename-2"
  "filename-n")

for demanding the success of parsing all n filenames and

(fails"Fact string."
  "filename-1"
  "filename-2"
  "filename-n")

for demanding the failure of parsing all n filenames.