WASM Build

[edge0701]

It would be nice to be able to compile to WASM, as per the PR #2.

I have tried building to WASM from the fork but I get the following error:
LinkError: WebAssembly.instantiate(): Import #41 module="env" function="_llvm_exp2_f64" error: function import requires a callable

I am compiling on ArchLinux using the latest emsdk.
The sed tasks in the Makefile also fail on my OS as it should be sed -i.bak i.e. without a space.

As you know, I can't create an issue on a fork, hence why I am raising it here.
I believe using WASM should increase the speed of ccv-js, which is important.

Great work so far @fta2012 and @shahrodkh, very impressive (:

[fta2012]

I played with a wasm build based on @shahrodkh's example back then. I just cleaned it up and pushed it. Let me know if that works for you.