Make it possible to override timeouts

Hi guys,

I propose the inclusion of the following change: merge :post-opts / :get-opts client parameter in post-points / get-query so that the socket and connection timeouts can be overridden.

I'm using some Fanout Continuous Queries within my InfluxDB server, so it seems the writes are a bit slower, which makes call to post-points timeouts. This PR makes it possible to override the read timeout by using a specific client property:

```
(def client (influx/make-client {:db "test_db"
                                 :post-opts {:socket-timeout 10000}
                                 :get-opts {:socket-timeout 2000}}))
```

Let my know what you think of this change.