Invalid references throw useless errors.

[jczerwinski]

References that citation-js cannot parse are ugly and should be improved. They look like this:

[set] This format is not supported or recognized
C:\Users\Jam\workspace\schol\schol\src\schol.js:58
          if (err) throw err;
                   ^

TypeError: Cannot set property '_original' of undefined
    at Object.keys.forEach (C:\Users\Jam\workspace\schol\schol\src\schol.js:177:21)
    at Array.forEach (<anonymous>)
    at buildBibliography (C:\Users\Jam\workspace\schol\schol\src\schol.js:168:21)
    at filenames.forEach.filename (C:\Users\Jam\workspace\schol\schol\src\schol.js:106:29)
    at Array.forEach (<anonymous>)
    at Ware.cite (C:\Users\Jam\workspace\schol\schol\src\schol.js:94:6)
    at Ware.<anonymous> (C:\Users\Jam\workspace\schol\schol\node_modules\wrap-fn\index.js:45:19)
    at next (C:\Users\Jam\workspace\schol\schol\node_modules\ware\lib\index.js:85:20)
    at Ware.run (C:\Users\Jam\workspace\schol\schol\node_modules\ware\lib\index.js:88:3)
    at Metalsmith.<anonymous> (C:\Users\Jam\workspace\schol\schol\node_modules\thunkify\index.js:43:12)