Fix bug where two editors on same screen affect content escaping

If you had two editors on the same screen, editors were subject to the content escaping of all of the prior editors on that screen
Persist the main editor's state (visual vs. text) regardless of FM

Without this, changing a FM editor's state from Viisual to Text (tinymce to html) would change the cookie value that WordPress stores for the main editor. Meaning that if a FM editor is changed from Visual to Text, the next time the main editor loads it will also be in Text mode.
Test that editors' content rendering don't affect other editors
Fix redirect where `$parent_slug` is empty in submenu context
Merge pull request #235 from alleyinteractive/editor-fixes

Fix editor bugs with the visual vs. text state
Use false instead of 0 for consistency
Merge pull request #236 from alleyinteractive/submenu-redirect-bug

Fix redirect where `$parent_slug` is empty in submenu context
Ignore code coverage report and svn
fix tab css
Prevent caching, tweak styles
Merge branch 'mattheu-fix-tab-css'