Upgrade to latest playdoh-lib and Django 1.5.6

* Update snippets.base.tests.TestCase:
  Test-utils got fixed upstream to initialize self.client.
[fix bug 984462] Change JsonSnippet.icon help text to 96x96.
[fix bug 1001379] Add JSONSnippet.weight.
Fix bug 1010499: Update playdoh-lib for Django 1.5.8.
Bug 1053842: Add Django to vendor-local and update to 1.5.9.
Fix bug 1054472: Use ETags to determine if we can send 304s.

Changes the fetch_snippets view to add ETags to outgoing responses that
are a hash of their content. It then uses the incoming ETags from
clients to determine what snippet content the client currently has 
cached, and whether new snippet content needs to be delivered or if a
304 can be sent to instruct the client to use their cached snippets.

This should allow us to increase the frequency of updates by lowering
the amount of data we need to send.
Fix issue with memcached keys being too large.

If we hash the client’s repr, its length becomes predictable!
Revert "Fix issue with memcached keys being too large."

This reverts commit ae7c428d4d355c2270d5139acebe464b925a00a5.
Revert "Fix bug 1054472: Use ETags to determine if we can send 304s."

This reverts commit b12f537e8f9b1de80dcc86d0814222d8cd595887.
Fix bug 1054472: Add ETag header to responses.
[fix bug 1059714] Add 'Save As' button for Snippets and JsonSnippets.

We force disabled=True for cloned snippets to avoid mistakes.
Merge pull request #60 from glogiotatidis/clone-2

[fix bug 1059714] Add 'Save As' button for Snippets and JsonSnippets.
Bug 1054410: Accommodate snippets with root tags w/o “snippet” class.

The JavaScript previously assumed that the parent element of the 
“snippet”-classed element had the metadata for a snippet, such as its
ID. Raw snippets may have an extra surrounding element for styling or
other reasons, and instead of mandating that the root element of a 
snippet be the snippet-classed element, this updates the JavaScript to
search for the closest parent element with the “snippet-metadata” class.
Add missing negation to check for class in snippet JS.

We should only keep searching up the chain if we haven’t found the 
metadata div yet.
Add sphinx_rtd_theme and docs for developing snippets.
[fix bug 1063585] Make 'about:accounts' snippet links to trigger showFirefoxAccounts Event.
Merge pull request #62 from glogiotatidis/clone-2

[fix bug 1063585] Make 'about:accounts' snippet links to trigger showFirefoxAccounts Event.
[bug 1063585] Lowercase tagName before comparing with 'a'.