If we do not have SimpleCov or Coveralls installed, we should be able to
continue with the rest of the test suite.
This allows the tests to run outside of Bundler if SimpleCov or
Coveralls are not installed.
Need to un-require and then re-require Docile after SimpleCov is
loaded, so that it can measure test coverage of the library. This
is necessary since SimpleCov began to ship with Docile as a
dependency.
Weirdly, on coveralls.io, only Rubinius (rbx-19mode) shows a 1%
lack in coverage due to a line in docile_spec.rb. This should
ensure that the spec files are never measured for code coverage.
Ken Dreyer