Initial whitespace cleanup
Reindent the feeds atom
Reindent the default options atom
Reindent ns form
Refactor parse-numbers

  - Rewrite nested ifs into a single cond
  - Remove dangerous use of read-string
  - Remove spurious use of boolean
Rewrite parse-for to use config data better

The existing parse-for was quite frankly shameful. The intermixing of
"parameterized" code via the exchange configuration atom and the
straight line hard coding of format strings made extension without
direct modification of library source impossible.

This patch corrects these failings by migrating the exchange specific
code into the exchange configuration structure so that a user can
reasonably add a new exchange without executing a massive and intrusive
library rewrite.
Tweak parse-numbers

 - Add a worthwhile docstring
 - Remove checks against specific Java classes in favor of Clojure core
   predicates which are more general
Refactor url-for

url-for was also an inexcusable straight line case monster. This patch
gives url-for the same treatment as parse-for and rewrites it so that
what little code was actually dependent on the particular exchange is
modularized out to be exchange specific and configurable.

 - Document url-for
 - Rewrite url-for cases into the config structure
 - Rewrite url-for itself accordingly
Rewrite http-opts-for

Part III of me killing off explicit inline configuration via straight
line code with explicit special cases. Need I go on?

 - Docstring
 - Sane config structure
Refactor callback for style
Refactor ticker for style
Reorder parse-numbers for the compiler's benifit
Merge pull request #5 from arrdem/master

Major rework