Use the node v8 promisify API to remove unnecessary code

[addityasingh]

• closes Use the node v8 promisify API to remove unnecessary code #153
• Use the node 8 promisify API to remove unnecessary code
• Polyfill it for older node versions

[vigneshshanmugam]

Please remove package-lock.json file

[addityasingh]

This is auto-generated by npm 5 to optimise the install time

[vigneshshanmugam]

I am aware of that, But we already use yarn.lock for determinism.

[codecov-io]

Codecov Report

Merging #157 into master will increase coverage by 4.78%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #157      +/-   ##
==========================================
+ Coverage   91.77%   96.55%   +4.78%     
==========================================
  Files          13       13              
  Lines         523      523              
  Branches       90       90              
==========================================
+ Hits          480      505      +25     
+ Misses         43       18      -25

Impacted Files	Coverage Δ
lib/fetch-template.js	97.22% <0%> (+69.44%)	⬆️

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[addityasingh]

Closing this for now, since there are some possible performance issue with the util.promisify library

[addityasingh]

Seems like wrong PR to me. I will close this and create a new 1

[vigneshshanmugam]

The title seems wrong here. But we need tests for fetch-templates as well :)