Initial support for network acls
get_all_network_acls now works properly
Removed extraneous comments.
Added support for associating and disassociating network ACLs and
subnets.
Added supoprt for replacing network acl entries.
Now properly populates NetworkAclEntry class with icmp & port range
options.
Removed unnecessary import of NetworkAclEntry.
Initial support for DBSubnetGroup
_sign_string private_key_file can now be file-like

Distribution._sign_string is now a little bit more flexible, allowing
the private_key_file to be a file-like object (or really anything with a
.read() method).
Added support for block device mappings in autoscaling groups (re #753, #1343)
updat incorrect copyright
Add missing function parameter (re: #1357)
add integration test
cloudformation Stack DisableRollback is always True

Fix problem where DisableRollback is always true, because
bool("False") == True
travis is secure by default now
Adding updated values for recurring autoscale operations
Adding updated documentation for the new variables
Fix #1146: return response from custom url opener

The previous fix for this (70e9ec) created a proxy opener
and retrieved metadata results, but then called urlopen(...)
and returned those results.  The end result was that you
were getting the proxied result, which is not what we want.

As a side effect of this bug, we were making twice as many
calls to the metadata service than we needed, once using
the custom opener we create, and once using urllib2.urlopen.

I've also added a unit test for this fix.  It's admittedly a bit
contrived, but it did fail before implementing the fix, and it
does pass now with the fix in place.
Only use 2 metadata service calls to get credentials

Because of the lazy loading dict returned when retrieving
IAM role credentials, we were making twice as many calls:

* .../meta-data/
* .../meta-data/iam/
* .../meta-data/iam/security-credentials/
* .../meta-data/iam/security-credentials/role-name

Instead the ``data`` arg is used so that we can make only two
calls, one to retrieve the role name, and one to retrieve the
actual credentials:

* .../meta-data/iam/security-credentials/
* .../meta-data/iam/security-credentials/role-name
added docs for param_group in rds modify
Updated requests to something more modern.