[minor] Add connection timeout to spec

This PR is related to the connection timeout issue discussed in #175.

In the javascript *Primus* implementation, the client-side timeout is always correct since the client library is generated by the server application. However, in the *Objective-C* implementation there is no way to know what this timeout is.

In short, the *Objective-C* implementation needs to set a sensible client-side timeout (*less than or equal to* the timeout defined on the server-side) to avoid being killed by the server.

I've exposed the timeout value on the `spec` endpoint and modified the respective tests.