Fix grunt pre-build error

[yosmoc]

Before

./node_modules/grunt/bin/grunt pre-build
secret/auth_code.json is not found. CodeSigning is not available.
Running "pre-build" task

Running "compile" task
node_modules/.bin/webpack --config webpack-production.config.js
Hash: ccaf27ad4bf2df5d3c4b
Version: webpack 1.15.0
Time: 24077ms
    + 969 hidden modules

ERROR in main.js from UglifyJs
SyntaxError: Unexpected token punc «,», expected punc «:» [./~/markdown-it-plantuml/lib/deflate.js:6,0]

ERROR in finder.js from UglifyJs
SyntaxError: Unexpected token punc «,», expected punc «:» [./~/markdown-it-plantuml/lib/deflate.js:6,0]


Running "pack:osx" (pack) task
/Users/yoshi/src/github.com/yosmoc/Boostnote/dist
Packaging app for platform darwin x64 using electron v1.6.15

Done.

After

./node_modules/grunt/bin/grunt pre-build
secret/auth_code.json is not found. CodeSigning is not available.
Running "pre-build" task

Running "compile" task
node_modules/.bin/webpack --config webpack-production.config.js
Hash: 96f1d33ce56d038a4b30
Version: webpack 1.15.0
Time: 35587ms
    Asset     Size  Chunks             Chunk Names
  main.js   2.2 MB       0  [emitted]  main
finder.js  1.72 MB       1  [emitted]  finder
    + 968 hidden modules


Running "pack:osx" (pack) task
/Users/yoshi/src/github.com/yosmoc/Boostnote/dist
Packaging app for platform darwin x64 using electron v1.6.15

Done.

[kazup01]

LGTM

[kazup01]

Merged. Thank you for your contribution!