Jonahstanley/upgrade chrome version

suggested reviewers: @singingwolfboy @jzoldak 
The following features had issues with chrome/chrome driver versions

lms/djangoapps/courseware/features/homepage.feature
cms/djangoapps/contentstore/features/advanced-settings.feature
cms/djangoapps/contentstore/features/html-editor.feature
cms/djangoapps/contentstore/features/problem-editor.feature
cms/djangoapps/contentstore/features/section.feature
cms/djangoapps/contentstore/features/subsection.feature
cms/djangoapps/contentstore/features/upload.feature
cms/djangoapps/contentstore/features/video-editor.feature
cms/djangoapps/contentstore/features/video.feature

In order to fix these, the following things were changed:
1. In homepage.feature, partners could no longer be accessed with .text or .value so .html was used
2. Code mirror was very awkward to deal with and the place to accept user input is technically hidden so by making it visible, the previous interaction could be kept.
3. The other issues were fixed by adding implicit waits and success conditions to clicks.  These were mostly failing due to animation speeds.  One of the animation endings could only be detected through its styling, thus the evaluate_script is used in order to access it.

These changes were tested in chrome version 28.0.1500.71 and chromedriver 2.1.210398
testing.md was updated accordingly.  It is also important to note that this version of chromedriver is compatible with versions 27-30 meaning that it won't work with chrome 26 (what a lot of people might be running) explaining why both need to be updated at once.

All changes that were made should be backwards compatible due to the nature of the changes (since mostly only verification steps were added).  world.wait_for is an implicit wait so these tests shouldn't take any longer to run.