* Added top-level test for the executable command.
* Running `rake' now runs all specs.
* Fixed top-level test.

1. Wrong thing was compared with the canonical executable output.
2. Canonical output had leading whitespace.
* Added reading/writing to the executable.

...to ensure all is fine with that.
* Introduce Robot class scaffolding.

Also, remove stripping of input for now as we don't have any use for it yet.
* Pass top-level test by doing the minimum.

As I understand now, this top-level test is just for testing reading/writing of
the executable.
* Start on tests for Robot class.
+ PLACE command works.

Also, disable top-level test for now as it fails. I have more work to do
regarding PLACE command at unit test level.
* Refactor. Better test comment.
* Rename spec file.

It's the common spec for the executable and library.
* Test for invalid PLACE command (the command is ignored).
* Another invalid PLACE command test.
* Refactor tests.
* Another invalid PLACE command test.

This time check facing direction.
+ PLACE recognizes EAST, SOUTH, WEST facing directions.
* Refactor. Prepare to check coordinates passed to PLACE.
+ Ignore PLACE command with x > table width.
* Refactor.
* Refactor.

Check whether passed x, y coords are integer and convert to Integer in one go.
* Refactor. Added parse_place_command method.