swap in patron for typhoeus

Regarding https://github.com/oscardelben/firebase-ruby/issues/32, the new benchmark shows improvement, cafe internet and all. 

```sh
$ ruby bench.rb 

Rehearsal ------------------------------------------------
curl           0.000000   0.000000   0.050000 (  0.993876)
patron         0.020000   0.010000   0.030000 (  0.483353)
firebase gem   0.010000   0.000000   0.010000 (  0.453753)
--------------------------------------- total: 0.090000sec

                   user     system      total        real
curl           0.000000   0.000000   0.040000 (  0.490606)
patron         0.010000   0.000000   0.010000 (  1.978371)
firebase gem   0.020000   0.000000   0.020000 (  0.464875)
```
So, the problem with this is that it makes the Firebase object not thread-safe. If you try to use a global firebase handle in your app and have multiple worker threads in Sidekiq, libcurl will crash. What do you think about making the sessions created per-request?