feat: add options validation (schema-utils)

[michael-ciniawsky]

Notable Changes

This PR removes the obsolete options handling for this.options.fileLoader (webpack =< v1.0.0)

webpack.config.js

const config = {
  module: {
    loaders: [
     { 
        test: /\.(png|jpg)$/,
        loader: 'file-loader'
      }
    ]
  },
  fileLoader: {...options} // Invalid in webpack >= v2.0.0
}

[codecov]

Codecov Report

Merging #184 into master will decrease coverage by 0.46%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #184      +/-   ##
==========================================
- Coverage   97.43%   96.96%   -0.47%     
==========================================
  Files           2        2              
  Lines          39       33       -6     
  Branches       18       16       -2     
==========================================
- Hits           38       32       -6     
  Misses          1        1

Impacted Files	Coverage Δ
src/index.js	100% <100%> (ø)	⬆️

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[alexander-akait]

👍