solidity compiler settings in project.json don't work as expected

* Populus Version: on master
* OS: OSx

### What was wrong?
providing any `command_line` option like `evm_version` in the example below doesn't work
```
"SolcAutoBackend": {
"class": "populus.compilation.backends.SolcAutoBackend",
"settings": {
"optimize": true,
"command_line_options": {
"allow_paths": "/",
"evm_version": "homestead"
}
}
```
This is because populus uses `standard-json` as input to `py-solc`:
https://github.com/ethereum/populus/blob/c256cbac0e343a1ce477a2e6128ef6a6c77b8c3c/populus/compilation/backends/solc_standard_json.py#L134-L145
Whenever `standard-json` is passed to `py-solc` all other options are ignored.
```
$solc --help
...
--standard-json Switch to Standard JSON input / output mode, ignoring
all options. It reads from standard input and provides
the result on the standard output.
...
````

#### Cute Animal Picture


Start in populus/compilation/backends/solc_standard_json.py at the referenced lines and reproduce the project.json configuration with command_line_options such as evm_version. Trace how py-solc receives standard-json input and verify that the requested compiler settings are honored rather than ignored.

Written by the indexing model from the issue text.