WIP: replace request by axios (#144)

[guimard]

It works except a test. Error is:

  28 passing (4s)
  1 failing

  1) correctly caches remote files:
     Uncaught Error: ENOENT: no such file or directory, open '/millstone/test/cache-url.mss'
  



(node:3820402) UnhandledPromiseRejectionWarning: Error: ENOENT: no such file or directory, open '/millstone/test/cache-url.mss'
(node:3820402) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
(node:3820402) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
npm ERR! code 1
npm ERR! path /tmp/tt/millstone
npm ERR! command failed
npm ERR! command sh -c mocha -R spec --timeout 10000

[guimard]

Help needed to understand this error