makes rename-symbol sync again

- implies that ASTs are cached in refactor-nrepl
Remove outdated commentary
Add cljr-remove-let

It's likely that we have to re-implement this in the middleware, but
since `find-usages` doesn't work on locals atm this will have to do.
Don't clean dev/user.clj when running project-clean
fixes bug in resolving symbol if comes from

... aliased ns and forces using project dir for find symbol if find
symbol is used for warming the cache
Don't use find-file non-interactively

Closes #99
If there is an open buffer for filename, then change that.

Otherwise open the file and do the changes non-interactively.

Ref #99
Avoid triggering clojure-mode-hook
warms the AST cache after rename symbol and

... adds sections in README about find usages and rename symbol

- cache warming only can be done if the ns defining the renamed symbol
  was loaded -- otherwise there is no way via cider to find out where
  the renamed symbol was defined
Merge pull request #100 from clojure-emacs/add-cljr-remove-let

Add cljr-remove-let
Make cljr--sort-project-dependencies more robust

* Preserve comments at EOL and above dependency vectors
* Preserve metadata
* Dependency vectors spanning multiple lines

Closes #73