Add test coverage and benchmarks

[maxgillett]

The current code is missing unit and integration tests for a large number of components, and the example cannot be run in the current commit due to a breaking change (see issue #18). A factorial and fibonacci benchmark are present in the benchmark branch, and could be merged in to the main repository, but other benchmarks should be added to the speed of proof generation when using the Cairo VM. The WASM folder should also be moved to a tests/examples folder.