[Fix #631] Set file and line metadata when doing interactive evaluation
[#631] Track column number in interactive eval

A small present for the awesome @cemerick :-)
Simplify dummy contents generation

As suggested by @vitoshka.
Observe `cider-stacktrace-print-level` for test errors.

Pass the `cider-stacktrace-print-level` defcustom added in 2142ee5 when viewing
stacktraces for test errors.

Also, change `if` to a `when` to clarify intent.
[Fix #776, #773, #733] Rewrite bencode decoder

  - nREPL dicts are now plists and accessor api is given by `nrepl-dict-p`,
    `nrepl-dict-get` and `nrepl-dict-put`.
  - nested stack is used for decoded messages to avoid re-parsing of incomplete messages
  - queues are used for raw strings from server and for decoded requests
Merge pull request #778 from vitoshka/bencode

[Fix #776, #773, #733] Rewrite bencode parser