Executable refactoring and no_std support

[sorpaas]

• Move executables to separate crates. In this way, we can get minimal dependencies for core util library.
• Add no_std support for core util library. In particular, BTree map and set will be used when in no_std.
• Temporarily depend on git version of parity-wasm until no_std is released.

Closes #76

[lexfrl]

just tried to cargo install.cargo install is not looking trough workspace for binaries.
https://github.com/paritytech/wasm-utils#build-tools-for-cargo

cargo install
error: no packages found with binaries or examples

I'm not sure, maybe it will still work in case if we install it from crates.io though

[sorpaas]

@fckt Yeah looks like after splitting the executable, it would need to be installed individually. rust-lang/cargo#4101

[pepyakin]

AFAIR, we already using cargo install pwasm-utils --bin wasm-build for quite some time? Or am I missing something?

[NikVolf]

we will have to publish every binary package separately?

[sorpaas]

@NikVolf Yes, but we can also combine it together. Which way do we prefer?

[NikVolf]

Yeah, i think all executables should be in one place at least.

Package "pwasm-utils-cli" would be great

[NikVolf]

Looks cool, though @pepyakin wants to play with it before it's merged?

[pepyakin]

Already playing, looks good so far : )

[lexfrl]

We should make sure the install command will continue to work. Otherwise we have to edit .travis.yml's in all projects which are using wasm-build

[NikVolf]

@fckt not a big deal, we'll just have to change to cargo install pwasm-utils-cli

[pepyakin]

Great!

[pepyakin]

But can we release parity-wasm and use the released version there?

UPD: Done!