Options parameter in files.getFiles() is now optional

In spec, options parameter appears to be optional (https://github.com/pkgcloud/pkgcloud/blob/master/docs/providers/rackspace/storage.md#clientgetfilescontainer-options-functionerr-files--), however if null is passed, the method generates "TypeError: Cannot read property 'limit' of null".
default header check
bulk delete
Adding Openstack Cinder Support
1.0.2
Merge branch 'master' into pr/320
Adding null option handles for amazon, azure
Cleaning up Rackspace references in openstack providers

- Fixes #338
Adding more details to options required for creating a client to rackspace

- Part of #337
Cleaning up the options for the openstack createClient docs

- Part of #337
Adding a note on the openstack README

- Part of #337
Adding a missing region to rackspace compute-getting-started

- Part of #337
Adding regions list to rackspace docs
accept both string and File values and explicit callback for bulk delete
Minor style cleanup
Merge branch 'pr/342'
Merge pull request #340 from kidozen/pr1

default header check
Cleaning up Amazon docs
Merge remote-tracking branch 'upstream/master'