Update README

Update the README file to include some more usage info.

Change-Id: I25f6750410b35158f521e96f73bad5df1e8e0963
Partial-Bug: #1314873
Fix log_curl_request API version duplication

log_curl_request duplicates API version when logging request (e.g.
http://192.168.122.222:6385/v1/v1/nodes/detail). Trailing API version
should be removed from the ironic endpoint when constructing logged
string.

Closes-bug: #1395740
Change-Id: Ia3fc29ed0ccaf2fbe9fea041098dcf079d711e8f
Add IRONIC_URL to README

Adds an example of pointing the client at a different Ironic API
endpoint.

Change-Id: Icd50d40184838d383c1c194d9051ee36acb3c01a
Merge "Fix log_curl_request API version duplication"
Merge "Update README"
Merge "Add IRONIC_URL to README"