Handling issue #52

Many consumers of the compute service uses 'OS-EXT-IPS:type' field,
which is easy to support as SL always assigns private
(primaryBackendIpAddress) and public (primaryIpAddress) IPs which can be
categorized into 'fixed' and 'public' respectively.
Fixed public ip type

Public IP is known as floating IP in OpenStack changed public type to
floating.
Generates new token from old token.

The API Specification http://api.openstack.org/api-ref-identity.html allows users to authenticate and generate token from old token.
Request body format:
    {
        "auth" :
            { "token" : {"id" : "old_token"} }
    }

such request:
    1. validates the token
    2. decodes the token
    3. and generates new
Username/Credentials retrived from token driver

Since each token driver is free to use the way it wants to store the
username/password, username() and credential() method are invoked to get
the values. token_driver.credentials() added in view of this need.
Removed _is_token_auth()

If request contains token id it is assumed to be token auth.
Made primaryIpAddress as fixed.

The primaryIpAddress is static and doesn't change during its life-cycle,
it was more appropriate to keep it as 'fixed' instead of 'floating'. The
portable IP from SoftLayer makes more sense for 'floating' IP.
Merge branch 'master' into ip.type
Merge pull request #59 from amol/token-using-token

Generates new token from old token.
Merge pull request #53 from amol/ip.type

Handling issue #52