Doc changes for new pip-requirements

dnspython was added recently to the list of requirments.

This patch completes the change:
1. The new requirement is documented
2. The need for tox --recreate is documented
(assuming there is no way to automate 2 above)

Change-Id: I49f0cb4b01b79dd7cf4329984a2f8416378ebe19
Fixes: Bug #1176627
Fixed issue with use of delimiter in container queries.

Currently if you have a container with objects named
x/y and x0 and you use delimiter=/ in your query, x0
will be excluded from the results. This patch resolves
this problem.

To replicate the original issue, create a container
called 'test' with the following objects:

x/y
x0
x1

Then do a GET with 'accnt/test?delimiter=/' and the
following is returned:

x/
x1

i.e. x0 is missing from output.

Change-Id: If196e3075612b121ef8da4a9128167d00a248c27
have tempurl allow OPTIONS requests

Change-Id: I431cac1e9818a335ff8d20288ab6acf39d6b6d5e
Merge "have tempurl allow OPTIONS requests"
Allow 2 TempURL keys per account.

This allows users to rotate their TempURL keys without invalidating
all existing signed URLs. This is handy if you have multiple systems
generating signed URLs, but you want to change your keys for some
reason (e.g. keys compromised, company policy, general paranoia).

Both the first and second keys are optional, so existing accounts'
signed URLs will continue to work as before.

This commit does change the memcache key used to store the fetched
TempURL keys. This is because we were storing the old key as a string
in memcached, but the new one is a list of keys. Since the key cache
lifetime here is only 60 seconds, it doesn't seem like too big a deal
to completely flush the TempURL cache.

Also, this commit adds caching of a negative TempURL result. If the
account HEAD reveals no TempURL keys at all, that result is now stored
for 60 seconds the same way that a positive result would be.

Change-Id: I40a02bd607283fbce11aa52a9bb8a5846ab17f5e
Merge "Doc changes for new pip-requirements"
Merge "Allow 2 TempURL keys per account."