Add linting and coverage

[abrahamq]

we use eslint with google's linting package to maintain code consistency across the bots, see: https://github.com/urbanriskmap/cognicity-reports-facebook/blob/master/package.json \

for details

[abrahamq]

looks like there's now a eslint rc, but it doesn't pass + there's no npm lint script specified. Please let me know via slack if you have questions/ need help with anything

abrahamq@abrahamq-XPS-8700:~/cognicity-reports-line$ eslint src/

/home/abrahamq/cognicity-reports-line/src/config.js
   3:1  error  Unexpected var, use let or const instead       no-var
  12:1  error  Line 12 exceeds the maximum line length of 80  max-len

/home/abrahamq/cognicity-reports-line/src/function/receive/index.js
  1:1  error  Parsing error: The keyword 'import' is reserved

/home/abrahamq/cognicity-reports-line/src/lib/linebot.js
  1:1  error  Parsing error: The keyword 'import' is reserved

✖ 4 problems (4 errors, 0 warnings) ```