[Fix #31] load-file should return value of last expression

[danskarda]

For detailed discussion see #31 and clojure-emacs/cider#830

[danskarda]

Second commit adds a support for in-ns during loading. Without support for in-ns, ClojureScript eval is slow in CIDER.

@cemerick Please, please, pretty please, merge the fix and release new version. Without it ClojureScript evaluation is second class citizen in CIDER: slow and without results and exceptions. Unfortunately both issues are result of your solution proposed in http://dev.clojure.org/jira/browse/NREPL-59

/cc @bbatsov

[bbatsov]

@cemerick I think that the second commit in the PR is pretty sensible. There's nothing bad in supporting in-ns during load-file, right?

[cemerick]

Reopening to consider the in-ns issue later.

[cemerick]

I released 0.2.0 today, which is effectively a rewrite in order to accommodate the upstream changes in ClojureScript's provided REPL machinery. This has eliminated many, many issues caused by piggieback's previous implementation (both in the details and strategy). Closing this now, since the environment is entirely different now (load-file is implemented as its own operation, not a transform over arguments to the default Clojure load-file impl, etc).