Fix development dependencies

npm install did not work because of missing coffee-script so it was
included in devDependencies. Also corrected the key from
dev-dependencies to devDependencies.
Added (currently failing) test for sort()

Added a test that verifies sorting works as expected. Currently this
test will fail.
Fix sortSyntax

sortSyntax handled the given "naturalMongoSyntax" as an array even if
documentation states it is an object. Fixed to handle as object.

Now "cursor.sort({field:1})" actually sorts.
Merge pull request #22 from vesse/master

Fix sort() function