Fix solc usage

[phahulin]

poa-bytecode script require('solc'), but solc dependency is missing in the package.json.

Also, MoC instruction emphasizes on step 2 that binary solc is required (not the one from npm) https://github.com/poanetwork/wiki/wiki/Master-of-Ceremony-Setup#poa-network-consensus-contract
but it's probably outdated and doesn't seem to work anyway (solc from npm is still required to run the script).

It needs to be clarified if solc binary should be installed separately and how to use it + if npm module is also required, package.json should be updated.

[varasev]

poa-bytecode script require('solc'), but solc dependency is missing in the package.json.

Yes, I added solc into scripts/package.json in #139 - it's waiting for approval.

It needs to be clarified if solc binary should be installed separately and how to use it

@rstormsf @vbaranov please, take a look at step 2 on this page - is it still required to use solc not from npm for some reason? What's the reason to use binary package for solc instead of npm's?

[vbaranov]

@varasev we were using a binary package of solc because it was a requirement of using Python Solidity flattener. I think we shouldn't depend on it anymore. Instead, we could use truffle-flattener or POA Solidity flattener 😄, the first one is more preferable because it has an npm package. I guess we could change flattener in frames of #139 PR and also change README sections:

1. Prerequisites section
2. Start POA Network section

After that we could change a wiki guide

[varasev]

@vbaranov I tried to install truffle-flattener, but the last version of its package (v1.2.5) contains a critical vulnerability. I propose not to change flattener until we see a new safe version.

[varasev]

Done in #139.