translation of yaml to json is buggy

I noticed when specifying stoploss in the yaml when you do the following for one instance:

`      minimal_roi:
        '0': 0.015
`

it gets translated into json to this:

`
    "minimal_roi": [
        0.015
    ],
`
which should be
`
    "minimal_roi": {
        "0": 0.015
    },
`

So in general, probably this is not recognized as a numeric but rather a boolean value 