Silence the `say` methods by setting ENV var

This allows "silencing" the `say` methods by simply setting the
ENV var `CAPUTIL_SILENCE_SAY`. This is useful for test suites so
you don't get these message printed out while your tests are run.

Closes #3
Merge pull request #5 from redding/jcr-silence-say-methods

Silence the `say` methods by setting ENV var