add .npmignore file to not include sample in npm
mark express and mu2 as devDependencies

these are used for the sample. they are not needed for the library itself.
perhaps consider moving the sample to its own repository
Merge pull request #4 from omsmith/packaging

Packaging
(fix) params is a hash, not an array
Merge pull request #5 from omsmith/params

(fix) params is a hash, not an array
assume nodejs and provide browser build with browserify
parse url params using url module
use url module to build targetUrl