[TEST] Provide Functionality to Create Examples from Local Source

[ghost]

GithubExamples.initialize() is directly coupled to raw.githubusercontent.com, the "examples" are downloaded from there.

It should be possible to load the examples from the local file-system (e.g. offline-work, test-sequences etc.).

This should be either implemented directly into ethpm or as a quick workaround for the current problems within #87.

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Workaround

replace the get function within GithubExamples.initialize() to something like this:

  get: function(examples_path,callback) {
    var filename = path.join("./node_modules/ethpm-spec/examples" + examples_path);
    var content  = '';

    fs.readFile(filename, function(err,content) 
    {
      if (err)
        callback(err);
      else
        callback(null, content);
    });
  }

[ghost]

Closing in favor of housekeeping!!! (@cgewecke )