Find source locations even when clojure doesn't report them.

     Also, enhance `cider-jump-to` to accept the char location.
Merge pull request #693 from vitoshka/stack-nav

Find source locations even when clojure doesn't report them.
[#693] Add a changelog entry
Derive stacktrace-mode from special-mode
[#693] Correct the logic for interactively eval-ed defs lookup
[#631] Workaround for missing var metadata

Interactively evaluated var definitions lack metadata, so we can't
easily navigate to them. To workaround this we look for definitions
in open Clojure buffers.
Refine cider-locate-def

It now goes to the start of a matched definition.
cider-jump-to: Always jump to absolute line number, refs #737

Fixes invalid line offsets, when the buffer was already visited and the current
line number position is > 1
Remove non-interactive use of goto-line, refs #737
Merge pull request #737 from juergenhoetzel/fix-cider-jump-to

cider-jump-to: Always jump to absolute line number
Simplify a bit of code
Add Cygwin support. Refs #735

`cider-from-nrepl-filename-function` and
`cider-to-nrepl-filename-function` are used to translate from/to nrepl
filenames.

Add a default implementation on Cygwin systems utilizing "cygpath". Use
`identity` otherwise.
Merge pull request #735 from juergenhoetzel/cygwin

Cygwin support
[Fix #671] Remove problematic :init-ns related code
Get Clojure and nREPL versions from describe-session's response
[#671] Retrieve Java version from nREPL's describe session
[#671] Check middleware compatibility asynchronously
[Fix #739] Require clojure.tools.namespace.repl before using it
Correct compatibility check
Fix a small problem with the middleware compatibility check