Fix some typos in the workbench crash course.
Merge pull request #136 from MatthieuDartiailh/workbench-course-fixes

Fix some typos in the workbench crash course.
Merge branch 'master' of https://github.com/nucleic/enaml

* 'master' of https://github.com/nucleic/enaml:
  Fix some typos in the workbench crash course.