doc: remove Caine section from contributing guide

Caine bot is not active on the repository anymore.
This section is just confusing for new contributors.

Fixes: #802
PR-URL: #804
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

CONTRIBUTING.md

@@ -222,55 +222,3 @@ CoC](https://github.com/rust-lang/rust/wiki/Note-development-policy#conduct).
 * Avoid the use of personal pronouns in code comments or
   documentation. There is no need to address persons when explaining
   code (e.g. "When the developer")
-
-
-## Caine's Requirements
-
-Hello!
-
-I am pleased to see your valuable contribution to this project. Would you
-please mind answering a couple of questions to help me classify this submission
-and/or gather required information for the core team members?
-
-### Questions:
-
-* _Issue-only_ Does this issue happen in core, or in some user-space
-  module from npm or other source? Please ensure that the test case
-  that reproduces this problem is not using any external dependencies.
-  If the error is not reproducible with just core modules - it is most
-  likely not a io.js problem. _Expected: `yes`_
-* Which part of core do you think it might be related to?
-  _One of: `debugger, http, assert, buffer, child_process, cluster, crypto,
-  dgram, dns, domain, events, fs, http, https, module, net, os, path,
-  querystring, readline, repl, smalloc, stream, timers, tls, url, util, vm,
-  zlib, c++, docs, other`_ (_label_)
-* Which versions of io.js do you think are affected by this?
-  _One of: `v0.10, v0.12, v1.0.0`_ (_label_)
-* _PR-only_ Does `make test` pass after applying this Pull Request.
-  _Expected: `yes`_
-* _PR-only_ Is the commit message properly formatted? (See
-  CONTRIBUTING.md for more information)
-  _Expected: `yes`_
-
-Please provide the answers in an ordered list like this:
-
-1. Answer for the first question
-2. Answer for the second question
-3. ...
-
-Note that I am just a bot with a limited human-reply parsing abilities,
-so please be very careful with numbers and don't skip the questions!
-
-_In case of success I will say:_ `...summoning the core team devs!`.
-
-_In case of validation problem I will say:_ `Sorry, but something is not right
-here:`.
-
-Truly yours,
-Caine.
-
-### Responsibilities
-
-* indutny: crypto, tls, https, child_process, c++
-* trevnorris: buffer, http, https, smalloc
-* bnoordhuis: http, cluster, child_process, dgram