Logging treq requests (ready for review)

Log all treq requests

Filtering the logs, this produces logs like:

```
{
  "request_time": 0.1938619613647461, 
  "level": 6, 
  "url": "https://ord.servers.api.rackspacecloud.com/v2/851153/images/0d589460-f177-4b0f-81c1-8ab8903ac7d8", 
  "status_code": 200, 
  "facility": "treq.request", 
  "headers": "Headers({'via': ['1.1 Repose (Repose/2.12)'], 'content-encoding': [''], 'x-compute-request-id': ['req-aad11d46-a900-4f5a-a00e-6e30ba04b2ae'], 'server': ['Jetty(8.0.y.z-SNAPSHOT)'], 'date': ['Wed, 18 Dec 2013 00:36:43 GMT'], 'content-type': ['application/json']})", 
  "host": "ubuntu", 
  "full_message": "Request to get https://ord.servers.api.rackspacecloud.com/v2/851153/images/0d589460-f177-4b0f-81c1-8ab8903ac7d8 resulted in a 200 response after 0.193861961365 seconds.", 
  "version": "1.0", 
  "timestamp": 1387327003.782414, 
  "method": "get", 
  "short_message": "Request to get https://ord.servers.api.rackspacecloud.com/v2/851153/images/0d589460-f177-4b0f-81c1-8ab8903ac7d8 resulted in a 200 response after 0.193861961365 seconds."
}
2013-12-18_00:36:43.92187
{
  "request_time": 0.09945178031921387, 
  "level": 6, 
  "url": "https://ord.servers.api.rackspacecloud.com/v2/851153/flavors/2", 
  "status_code": 200, 
  "facility": "treq.request", 
  "headers": "Headers({'via': ['1.1 Repose (Repose/2.12)'], 'content-encoding': [''], 'x-compute-request-id': ['req-7aee4472-0be5-4a8e-9e60-980952c66f24'], 'server': ['Jetty(8.0.y.z-SNAPSHOT)'], 'date': ['Wed, 18 Dec 2013 00:36:43 GMT'], 'content-type': ['application/json']})", 
  "host": "ubuntu", 
  "full_message": "Request to get https://ord.servers.api.rackspacecloud.com/v2/851153/flavors/2 resulted in a 200 response after 0.0994517803192 seconds.", 
  "version": "1.0", 
  "timestamp": 1387327003.921659, 
  "method": "get", 
  "short_message": "Request to get https://ord.servers.api.rackspacecloud.com/v2/851153/flavors/2 resulted in a 200 response after 0.0994517803192 seconds."
}
2013-12-18_00:36:44.02278
{
  "request_time": 0.20078420639038086, 
  "level": 6, 
  "url": "https://ord.servers.api.rackspacecloud.com/v2/851153/images/0d589460-f177-4b0f-81c1-8ab8903ac7d8", 
  "status_code": 200, 
  "facility": "treq.request", 
  "headers": "Headers({'via': ['1.1 Repose (Repose/2.12)'], 'content-encoding': [''], 'x-compute-request-id': ['req-042bd766-e38c-4d82-af05-79c1d3fa27c9'], 'server': ['Jetty(8.0.y.z-SNAPSHOT)'], 'date': ['Wed, 18 Dec 2013 00:36:44 GMT'], 'content-type': ['application/json']})", 
  "host": "ubuntu", 
  "full_message": "Request to get https://ord.servers.api.rackspacecloud.com/v2/851153/images/0d589460-f177-4b0f-81c1-8ab8903ac7d8 resulted in a 200 response after 0.20078420639 seconds.", 
  "version": "1.0", 
  "timestamp": 1387327004.022637, 
  "method": "get", 
  "short_message": "Request to get https://ord.servers.api.rackspacecloud.com/v2/851153/images/0d589460-f177-4b0f-81c1-8ab8903ac7d8 resulted in a 200 response after 0.20078420639 seconds."
}
```