`StandardJSON` compilation backend does not correctly handle compiler settings

[pipermerriam]

• Populus Version: 1.8.x
• OS: osx/linux/win

What was wrong?

The populus.compilation.backends.SolcStandardJSONBackend does not correctly handle compiler settings.

Currently, the backend merges all compiler settings into the JSON input for compilation:

https://github.com/pipermerriam/populus/blob/3a0445e550baa344a0931a2b94f3c779c98505fe/populus/compilation/backends/solc_standard_json.py#L117

This is wrong as this config should only be updated with settings keys documented here: http://solidity.readthedocs.io/en/develop/using-the-compiler.html?highlight=standard-json#input-description

• remappings
• optimizer
• metadata
• libraries
• outputSelection

The rest of the settings should be passed into compile_standard as **kwargs

Cute Animal Picture

put a cute animal picture here.

[Netherdrake]

Is this still broken?