Make Truffle provider creation lazy

[frangio]

Fixes #1516
Fixes #1340

It seems like the creation of an HDWalletProvider object was blocking Truffle from exiting. I'm guessing this was because of some pending promise, probably related to a network connection that is started. This was completely unnecessary for the general use case of compiling or running the tests against Ganache, so I made the creation of this provider lazy using a JavaScript getter as seen here.

To be honest, I haven't tested the provider defined in this way. :-) I just know that it fixes the problem we were having.

[spalladino]

@frangio note that you can assign a function that returns the provider to the provider entry in the truffle config file, there is no need to create a custom getter. However, keep in mind that this may cause issues with nonce subproviders if you are using the hdwallet provider (see ConsenSys-archive/truffle-hdwallet-provider#65).

[frangio]

@spalladino Oh cool! Thanks, I'll use that feature.

[nventuro]

Yay, it works! From my local testing this also seems to fix #1340. How did you figure it out?

Regarding the fix, do we actually need to have the ropsten network defined? I'd remove the whole thing and drop the truffle-hdwallet-provider dependency, though it may be required for some obscure feature that I'm unaware of.

[frangio]

I removed most contracts and it still wasn't working and I just figured that the config was the only other thing that could be failing because I was told that other projects weren't having this problem.

Do we need any network other than ganache? I think we used them for EthPM deployment, but that wan't working anyway (though it may be fixable by now, see #824).

[frangio]

If you're sure that it fixes #1340 feel free to add the Fixes annotation to the description, but I don't have the context for that other issue.

[nventuro]

In that case I'd remove the ropsten config, and add it back when (if) the fix the EthPM issue, or any other issue that requires it.

[frangio]

Also removed the ganache network which was identical to development.

[nventuro]

Nice! Can we also get rid of truffle-hdwallet-provider?

[frangio]

Seems so!

[nventuro]

Looks like we have an implicit dependency on ethereumjs-util, can you explicitly install it?

[nventuro]

Awesome! 🎉