added simplistic e-mail test

fairly crude:

* not entirely sure what it is we're actually testing here
* test output includes "ERROR" (due to `ReportError` invocation), which
  will likely lead to confusion
* changing into package directory before running `go test` seems like
  smell
* setup and teardown should be separated from the actual test
* creating a mailx mock seems weird
* the "test/fixtures" directory seems inappropriate