add doc regarding CGI environment

most common vars in CGI environment explained
Merge pull request #133 from pkit/doc

add doc regarding CGI environment
objectquery: detailed docstring for `zerovm_query`

This adds a lot of detail about all of the response codes that can be
returned and the possible causes.
Merge pull request #136 from larsbutler/document-zerovm_query

objectquery: detailed docstring for `zerovm_query`
vagrant: improve the local dev env

The git clone on the host is now mapped in to the VM, and changes to the
code in the host dev environment will be reflected inside the VM (after
restarting devstack, of course).

This makes it a lot easier to experiment, debug, and test in a "real"
environment (and not just with the test suite).
Merge pull request #135 from larsbutler/vagrant-dev-env

vagrant: improve the local dev env
objectquery: add comment to explain 507 response
objectquery: fix content length mismatch cases

Previously, we only checked if the content-length header was not equal
to the amount of content received in a request. This resulted in a "499
Client Closed Request" (indicating a premature disconnect).

This response could be triggered by content either less then OR greater
than that specified in the conteint-length header. This is a bit weird.

This change alters the check and breaks it into two cases:

- actual content < content-length: 499
- actual content > content-length: 400 (Bad Request)

Tests are updated accordingly.
objectquery: 405 if container req is not GET

Containers can only be read by ZeroVM applications, thus "GET" is the
only supported method.

Previously, anything that wasn't a GET on a container resulted in a "400
Bad Request".