Extend the section on manually upgrading nREPL

Author: bbatsov

README.md

@@ -1037,9 +1037,17 @@ add this to your `profiles.clj`:
 {:user {:dependencies [[org.clojure/tools.nrepl "0.2.10”]]}}
 ```
 
+Make sure you add the newer nREPL dependency to the `:dependencies` key instead
+of `:plugins` (where `cider-nrepl` Lein plugin resides). That's a pretty common
+mistake.
+
 Generally you're advised to use the newest nREPL with CIDER, as bugs get fixed
 in pretty much every release.
 
+Note, that running `cider-jack-in` from outside the scope of a project will
+result in the **older (0.2.6) nREPL dependency being used** (at least on Leiningen
+2.5.1). This is likely a Leiningen bug.
+
 ## Documentation
 
 A single-page quick reference PDF for CIDER commands is available [here](doc/cider-refcard.pdf). This PDF can be created manually by running `pdflatex` on [the CIDER refcard LaTeX file](doc/cider-refcard.tex).