Replace deprecated  `__defineGetter__` and `__defineSetter__` syntaxes.

`__defineGetter__` and `__defineSetter__` are deprecated, use `Object.defineProperties` instead
Remove obsolete checking for preexisting setters
Test that an exception should be thrown if setter already exists
Add TODO for v0.7

Reminder to remove magic setters, deprecated since v0.6
Minor grammar correction in test notice
Check that hook redefinition includes hook name in raised exception
Replace deprecated __defineGetter__/__defineSetter

Use `Object.defineProperties` instead
Fixes #64

* remove-deprecated-define-getter-setter:
  Check that hook redefinition includes hook name in raised exception
  Minor grammar correction in test notice
  Add TODO for v0.7
  Test that an exception should be thrown if setter already exists
  Remove obsolete checking for preexisting setters
  Replace deprecated  `__defineGetter__` and `__defineSetter__` syntaxes.
Add test for empty suites exit code
Document exit code for improperly formatted suites
Use a promised version of fs.readdir when loading suites

Fixes #112
Improve error message for empty suites
Test error message on empty suites
Uniform exit codes for malformed suites
Ensure browser is quit if suite is malformed
Simplify error handling of unreadable suites
Allow time for browser startup in empty suite integration test
Handle loadAllFiles exceptions (fixes #112)

Ensure fs.readdir is called in the promise chain
Cover with integration test due to lack of SuiteLoader test suite

* handle-loadallfiles-exceptions:
  Allow time for browser startup in empty suite integration test
  Simplify error handling of unreadable suites
  Ensure browser is quit if suite is malformed
  Uniform exit codes for malformed suites
  Test error message on empty suites
  Improve error message for empty suites
  Use a promised version of fs.readdir when loading suites
  Document exit code for improperly formatted suites
  Add test for empty suites exit code
Add integration test for the behavior of the without config key
Add integration test to assert that it fails ignoring "not a feature"
Add a succeeding feature to the failing suite