Added a deprecation message and links to the Shaker GH repo and docs.
Made a copyedit.
Merge pull request #1057 from zhouyaoji/docs_deprecate_compile

[docs] Deprecated documentation for the `compile` command and linked to the Shaker docs.
Added note that ac.flash is asynchronous.
Updated the Selenium and made Firefox v20 a prerequisite. Also added a note that if you use different versions of either Firefox/Selenium, users should consult the platforms supported by Selenium.
Copy edited a note.