Replace old httpclient with requests

This review implements blueprint python-request and replaces the old
http client implementation in favor of a new one based on
python-requests.

Major changes:
* raw_request and json_request removed since everything is now being
  handled by the same method "_request"
* New methods that match HTTP's methods were added:
    - get
    - put
    - post
    - head
    - patch
    - delete
* Content-Type is now being "inferred" based on the data being sent:
    - if it is file-like object it chunks the request
    - if it is a python type not instance of basestring then it'll try
      to serialize it to json
    - Every other case will keep the incoming content-type and will send
      the data as is.
* Glanceclient's HTTPSConnection implementation will be used if
  no-compression flag is set to True.

Co-Author:  Flavio Percoco<flaper87@gmail.com>
Change-Id: I09f70eee3e2777f52ce040296015d41649c2586a