Previously, using `wasm-decompile` to decompile the Wasm bytecode on
the `wasm.html` example page gave this output:
```
export function fib(a:int):int {
if (a < 2) { return 1 }
return fib(a - 2) + fib(a - 1);
}
```
With this change the bytecode now decompiles to:
```
export function fib(a:int):int {
if (a <= 0) { return 0 }
if (a == 1) { return 1 }
return fib(a - 2) + fib(a - 1);
}
```
This means that the example page now prints the correct answer of 55 to
the console for `fib(10)`. Previously, `fib(10)` returned 89.
I also used `wasm-opt -Oz`, which removed an unnecessary `return`
instruction, saving 1 byte!
This impl is *extremely* simple, and is missing a lot of things, it's
also not particularly spec-compliant in some places, but it's definitely
a start :^)
