matchers: make the contain and match matchers useable.

Fix some silly bugs preventing these matchers from working
properly.
* src/specl.lua (matchers.match): Use VALUE consistently for
parameter name.
Set the return condition properly.
(matchers.contain): Likewise.
string.match patterns are not anchored, so no need to bookend
with .*.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
formatters: Be consistent when reporting met expectations.

* src/specl.lua (report): Add "Met" prefix to output.
(progress): Write "expectations met", not "examples worked".

Signed-off-by: Gary V. Vaughan <gary@gnu.org>