Put back in some older code to save source_code property.
Add helper method for typing in CodeMirror, make it robust to Mac and Unix.
Remove waits by adding code in click that will try the operation multiple times (thanks to Jonah).
Change the wording of problem steps to follow Given, When, Then... convention.
Change code to use css_click in hopes that will make the test pass on Don's mac.

css_click will try clicking multiple times.
Merge pull request #186 from edx/christina/latex_and_click

Bug fix for LaTeX source not saving