handle more eval commands used by SLIME in emacs

The Emacs SLIME implementation uses several variations of eval
for different purposes. These include slime-pprint-eval-region,
slime-interactive-eval, slime-eval-region, and several others.

The swank commands used by these eval functions include:
 - swank:eval-and-grab-output
 - swank:interactive-eval
 - swank:pprint-eval
 - swank:interactive-eval-region

I have implemented enough of each of these to satisfy SLIME
but they aren't full-featured.

swank:pprint-eval does not actually pretty print. It could
be implemented with racket's pretty-format function if an
s-expression form can be read from the repl instead of a string.
Merge pull request #2 from absurdhero/emacs-eval

handle more eval commands used by SLIME in emacs