Add travis and linting stuffs

[pdehaan]

This is a mildly weird repo. On one hand it seems to be getting stale w/ PRs and everybody working in branches, but on the other hand this repo seems to be our first "integration" point with new services.

I randomly noticed that we don't have a .travis.yml file in this repo, or seemingly any sort of JSHint/ESLint set up.

Here's the rough output from the "oauth" branch, using my preferred ESLint:

$ eslint .

oauth.js
   4:4   error  'crypto' is read only         no-undef
  43:31  error  db is defined but never used  no-unused-vars

retarget.js
  10:1  error  'crypto' is read only  no-undef

server.js
   18:15  error  Expected error to be handled                                    handle-callback-err
   68:0   error  Missing "use strict" statement                                  strict
   82:36  error  Trailing comma                                                  no-comma-dangle
  116:23  error  Use path.join() or path.resolve() instead of + to create paths  no-path-concat
    2:4   error  https is defined but never used                                 no-unused-vars

static/js/123done.js
  66:38  error  ev is defined but never used  no-unused-vars
  70:38  error  ev is defined but never used  no-unused-vars

static/js/state.js
   59:14  error  Missing semicolon            semi
   57:20  error  Missing semicolon            semi
   65:5   error  Unnecessary semicolon        no-extra-semi
   79:3   error  Unnecessary semicolon        no-extra-semi
  130:3   error  Unnecessary semicolon        no-extra-semi
  153:3   error  Unnecessary semicolon        no-extra-semi
  184:27  error  Missing semicolon            semi
  107:40  error  e is defined but never used  no-unused-vars
  170:40  error  e is defined but never used  no-unused-vars

✖ 19 problems

... And here's my .eslintrc file:

env:
  node: true
  browser: true

globals:
  $: false
  loggedInEmail: false
  state: false

rules:
  camelcase: 0
  curly: 0
  dot-notation: 0
  no-use-before-define: [1, nofunc]
  quotes: [0, single]

[pdehaan]

IIRC, the odd 'crypto' is read only error is because I have this defined as a Node+Browser project and the browser has a Window.crypto API so we have a soft collision. I could solve it by either using separate .eslintrc file for the "static/" subdirectory; or just setting browser:false and predefining window and document and localStorage globals — although now that starts to feel gross.