formatter: group and format expectations every example.

Fix a bug that counts a FAILed expectation incorrectly. Restart
the counter for every example, not just at the start of the
entire group.
* src/specl.lua (run_examples): Don't save up all the expectations
from the entire group before displaying, format them after every
example completes.
formatters: nicer fail message for report formatter.

* src/specl.lua (report.expectations): Reformat slightly for
better english, and to stand out better.