Make library PSR-1/2 compliant

Hi,

This PR does not introduce any BC nor does it add code. It juste:

* Replace tab by spaces in service description (also reduce from 8 to 4 spaces as it's easier to read)
* Make the whole code PSR-1/2 compliant (there was a ton of convention code errors)
* Add @method annotation on client so that IDE can auto-complete.

By the way, I'm wondering about the "addBatchEvents" in the KeenIO client. First, I think it's simply does not work (and should be removed/fixed) because it gets the "sendEvents" command which does not exist on the client (only "addEvents" exist). Secondly, it should be part of the client. This method is already define in the JSON service description, so providing a wrapper in the client is wrong. Either you should create a Service class that is a wrapper around the client, or you should remove this method from the client :).

If you agree, I can remove it (once again, as of today I really doubt this method is working anyway, so removing it won't introduce any errors...)

Thansks :)