Threescale agent header

Ok, so I did both 100 and 500 calls using both http and https endpoints. Results below:

100 Repeats:
![100x](https://cloud.githubusercontent.com/assets/1311133/4590970/445fe0fc-5066-11e4-86de-ccd262c251c5.png)

500 Repeats:
![500x](https://cloud.githubusercontent.com/assets/1311133/4590972/512a6636-5066-11e4-9630-073aeb091678.png)

Apart from the initial call and some spikes thereafter, it seems like the performance is similar.