Fix error handling and debug information with configuration files that are empty, or not present.

[EvanCarroll]

This does a few things.

Now if you have on config file you'll see the unthrown ECONFIGNOTFOUND error in your log:

  semantic-release:config SemanticReleaseError: Your release configuration file was NOT found
  semantic-release:config     at module.exports (/home/ecarroll/code/js/semantic-release/lib/get-error.js:6:10)
  semantic-release:config     at module.exports (/home/ecarroll/code/js/semantic-release/lib/get-config.js:42:12)
  semantic-release:config     at async module.exports (/home/ecarroll/code/js/semantic-release/index.js:257:32)
  semantic-release:config     at async module.exports (/home/ecarroll/code/js/semantic-release/cli.js:55:5) +0ms

The debug information no longer just shows the merged stuff, but also what the config file had in it. This is very useful if your config file is CommonJS and fixes #2152

  semantic-release:config Load config {
  semantic-release:config   filepath: undefined,
  semantic-release:config   unprocessed_config: undefined,
  semantic-release:config   processed_options: {
  semantic-release:config     branches: [
  semantic-release:config       '+([0-9])?(.{+([0-9]),x}).x',
  semantic-release:config       'master',
  semantic-release:config       'next',
  semantic-release:config       'next-major',
  semantic-release:config       [Object],
  semantic-release:config       [Object]
  semantic-release:config     ],
  semantic-release:config     tagFormat: 'v${version}',
  semantic-release:config     plugins: [
  semantic-release:config       '@semantic-release/commit-analyzer',
  semantic-release:config       '@semantic-release/release-notes-generator',
  semantic-release:config       '@semantic-release/npm',
  semantic-release:config       '@semantic-release/github'
  semantic-release:config     ],
  semantic-release:config     repositoryUrl: 'file:///home/ecarroll/code/trash/foo',
  semantic-release:config     _: [],
  semantic-release:config     n: true,
  semantic-release:config     debug: true,
  semantic-release:config     ci: true,
  semantic-release:config     '$0': 'semantic-release'
  semantic-release:config   }
  semantic-release:config } +2ms

And there is a new fatal Error that is throw if the file exists but it's empty EEMPTYCONFIG

Please verify your config file /home/ecarroll/code/trash/foo/release.config.js is present with content

SemanticReleaseError: Your release configuration was found but has no contents
    at module.exports (/home/ecarroll/code/js/semantic-release/lib/get-error.js:6:10)
    at module.exports (/home/ecarroll/code/js/semantic-release/lib/get-config.js:46:11)
    at async module.exports (/home/ecarroll/code/js/semantic-release/index.js:257:32)
    at async module.exports (/home/ecarroll/code/js/semantic-release/cli.js:55:5) {
  code: 'EEMPTYCONFIG',
  details: 'Please verify your config file /home/ecarroll/code/trash/foo/release.config.js is present with content',
  semanticRelease: true