WASM compatibility

[mankinskin]

If this crate was WASM compatible, it would be possible to serve WASM packages to web clients, running the crate locally. This could reduce overhead, as there was no server between client and exchange API.

[mankinskin]

Currently, cargo build --target=wasm32-unknown-unknown fails because of a dependency on net2, as described in this issue. And cargo tree reveals that this is a dependency because of tokio:

cargo tree | grep net2 -A 4 -B 20
│   │   │   │   └── hashbrown v0.8.2
│   │   │   │       [build-dependencies]
│   │   │   │       └── autocfg v1.0.1
│   │   │   │   [build-dependencies]
│   │   │   │   └── autocfg v1.0.1
│   │   │   ├── slab v0.4.2
│   │   │   ├── tokio v0.2.22
│   │   │   │   ├── bytes v0.5.6
│   │   │   │   ├── fnv v1.0.7
│   │   │   │   ├── futures-core v0.3.5
│   │   │   │   ├── iovec v0.1.4
│   │   │   │   │   └── libc v0.2.76
│   │   │   │   ├── lazy_static v1.4.0
│   │   │   │   ├── libc v0.2.76
│   │   │   │   ├── memchr v2.3.3
│   │   │   │   ├── mio v0.6.22
│   │   │   │   │   ├── cfg-if v0.1.10
│   │   │   │   │   ├── iovec v0.1.4 (*)
│   │   │   │   │   ├── libc v0.2.76
│   │   │   │   │   ├── log v0.4.11 (*)
│   │   │   │   │   ├── net2 v0.2.34   <<<<<<<<<<<<<<
│   │   │   │   │   │   ├── cfg-if v0.1.10
│   │   │   │   │   │   └── libc v0.2.76
│   │   │   │   │   └── slab v0.4.2
│   │   │   │   ├── mio-uds v0.6.8

There is an issue to make tokio support WASM, so I guess that would need to be resolved first: tokio-rs/tokio#1597