fix `npm install`
rename collection.js to index.js for convenience
Use native Array.isArray() where possible.

The use of Object.prototype.toString() was causing a slowdown when
first allocating a collection. We can instead use the much faster
`Array.isArray()` by checking for its presence and verifying its behavior.
remove redundant recursion
add preliminary benchmarks
Merge pull request #34 from codemix/benchmarks

Add preliminary benchmarks