Incremental docs publish, travis builds n more enhancements

[sivakumar-kailasam]

This PR introduces the following goodness,

• Travis scripts that publish incremental docs. Modified the module to skip processing any version of docs that already exists in the target DB
• Ability to run the module for a specific version of docs that can be passed as an arg. Eg node index.js 2.10
• YUIdocs were fetched twice from S3, the redundant call is removed
• Generate log msgs so that travis doesn't timeout
• Increase timeout between requests so that requests don't fail
• Removed unused deps, updated outdated ones & added npm script to fix file formatting using standard cli
• Added yarn.lock & editorconfig file

Things that requires travis org admin access,

• Enable travis for this repo
• Set the following,

  travis env set AWS_ACCESS_KEY_ID "$AWS_ACCESS_KEY_ID"
  travis env set AWS_SECRET_ACCESS_KEY "$AWS_SECRET_ACCESS_KEY"
  travis env set COUCH_USERNAME "$COUCH_USERNAME"
  travis env set COUCH_PASSWORD "$COUCH_PASSWORD"

• Replace the COUCH_URL in .travis.yml with actual db
• If the target couch db is a new one, we need to populate it with at least v1 docs since generating docs for both v1.x and v2.x takes more than 50mins which is the max period for travis builds.

Addresses ember-learn/ember-api-docs#66

[sivakumar-kailasam]

An additional step of flushing travis in heroku is to be added to the .travis.yml. Will raise it in another PR.