Switches to using compare endpoint

This is a pretty messy PR that just comments out the old behaviour and adds new stuff, feel free to take it as is or do your own - just wanted to get this out there


ref TryGhost/Ghost#4130

- uses githubs /compare/from..to endpoint
- processes commits into contributors
- excludes merges
- adds real name just cos
- adds first line of each commit for testing purposes

---

Example output from this PR for 0.5.0..0.5.1:
```
[ { commitCount: 9,
    name: 'ErisDS',
    realName: 'Hannah Wolfe',
    githubUrl: 'https://github.com/ErisDS',
    avatarUrl: 'https://avatars.githubusercontent.com/u/101513?v=2'
 },
  { commitCount: 4,
    name: 'felixrieseberg',
    realName: 'Felix Rieseberg',
    githubUrl: 'https://github.com/felixrieseberg',
    avatarUrl: 'https://avatars.githubusercontent.com/u/1426799?v=2'
},
  { commitCount: 1,
    name: 'jaswilli',
    realName: 'Jason Williams',
    githubUrl: 'https://github.com/jaswilli',
    avatarUrl: 'https://avatars.githubusercontent.com/u/214142?v=2'
 },
  { commitCount: 1,
    name: 'sebgie',
    realName: 'Sebastian Gierlinger',
    githubUrl: 'https://github.com/sebgie',
    avatarUrl: 'https://avatars.githubusercontent.com/u/539213?v=2'
    },
  { commitCount: 1,
    name: 'novaugust',
    realName: 'Matt Enlow',
    githubUrl: 'https://github.com/novaugust',
    avatarUrl: 'https://avatars.githubusercontent.com/u/1207005?v=2' } ]
```
> $ git shortlog -sn --no-merges 0.5.0..0.5.1
```
     9  Hannah Wolfe
     4  Felix Rieseberg
     1  Jason Williams
     1  Matt Enlow
     1  Sebastian Gierlinger
```

Which matches.. but then for 0.5.0..0.5.2-1 we get something with some commits from various parts of the tree missing:

```
contributors [ { commitCount: 76,
    name: 'JohnONolan',
    realName: 'John O\'Nolan',
    githubUrl: 'https://github.com/JohnONolan',
    avatarUrl: 'https://avatars.githubusercontent.com/u/120485?v=2' },
  { commitCount: 34,
    name: 'PaulAdamDavis',
    realName: 'Paul Adam Davis',
    githubUrl: 'https://github.com/PaulAdamDavis',
    avatarUrl: 'https://avatars.githubusercontent.com/u/390392?v=2' },
  { commitCount: 15,
    name: 'ErisDS',
    realName: 'Hannah Wolfe',
    githubUrl: 'https://github.com/ErisDS',
    avatarUrl: 'https://avatars.githubusercontent.com/u/101513?v=2' },
  { commitCount: 13,
    name: 'jaswilli',
    realName: 'Jason Williams',
    githubUrl: 'https://github.com/jaswilli',
    avatarUrl: 'https://avatars.githubusercontent.com/u/214142?v=2' },
  { commitCount: 12,
    name: 'felixrieseberg',
    realName: 'Felix Rieseberg',
    githubUrl: 'https://github.com/felixrieseberg',
    avatarUrl: 'https://avatars.githubusercontent.com/u/1426799?v=2' },
  { commitCount: 6,
    name: 'halfdan',
    realName: 'Fabian Becker',
    githubUrl: 'https://github.com/halfdan',
    avatarUrl: 'https://avatars.githubusercontent.com/u/176576?v=2' },
  { commitCount: 5,
    name: 'novaugust',
    realName: 'Matt Enlow',
    githubUrl: 'https://github.com/novaugust',
    avatarUrl: 'https://avatars.githubusercontent.com/u/1207005?v=2' },
  { commitCount: 3,
    name: 'hswolff',
    realName: 'Harry Wolff',
    githubUrl: 'https://github.com/hswolff',
    avatarUrl: 'https://avatars.githubusercontent.com/u/322576?v=2' },
  { commitCount: 3,
    name: 'rwjblue',
    realName: 'Robert Jackson',
    githubUrl: 'https://github.com/rwjblue',
    avatarUrl: 'https://avatars.githubusercontent.com/u/12637?v=2' },
  { commitCount: 2,
    name: 'SiR-DanieL',
    realName: 'Nicola Mustone',
    githubUrl: 'https://github.com/SiR-DanieL',
    avatarUrl: 'https://avatars.githubusercontent.com/u/4429413?v=2' },
  { commitCount: 2,
    name: 'jillesme',
    realName: 'Jilles Soeters',
    githubUrl: 'https://github.com/jillesme',
    avatarUrl: 'https://avatars.githubusercontent.com/u/2955483?v=2' },
  { commitCount: 1,
    name: 'studioromeo',
    realName: 'Robert Rhoades',
    githubUrl: 'https://github.com/studioromeo',
    avatarUrl: 'https://avatars.githubusercontent.com/u/846587?v=2' },
  { commitCount: 1,
    name: 'cobbspur',
    realName: 'cobbspur',
    githubUrl: 'https://github.com/cobbspur',
    avatarUrl: 'https://avatars.githubusercontent.com/u/4405395?v=2' },
  { commitCount: 1,
    name: 'JoshWillik',
    realName: 'Josh Vanderwillik',
    githubUrl: 'https://github.com/JoshWillik',
    avatarUrl: 'https://avatars.githubusercontent.com/u/2429492?v=2' },
  { commitCount: 1,
    name: 'wjake',
    realName: 'Jake Wright',
    githubUrl: 'https://github.com/wjake',
    avatarUrl: 'https://avatars.githubusercontent.com/u/4590364?v=2' },
  { commitCount: 1,
    name: 'sebgie',
    realName: 'Sebastian Gierlinger',
    githubUrl: 'https://github.com/sebgie',
    avatarUrl: 'https://avatars.githubusercontent.com/u/539213?v=2' },
  { commitCount: 1,
    name: 'blia',
    realName: 'Kirill Yakovenko',
    githubUrl: 'https://github.com/blia',
    avatarUrl: 'https://avatars.githubusercontent.com/u/242004?v=2' },
  { commitCount: 1,
    name: 'pedro-teixeira',
    realName: 'Pedro Teixeira',
    githubUrl: 'https://github.com/pedro-teixeira',
    avatarUrl: 'https://avatars.githubusercontent.com/u/1923771?v=2' },
  { commitCount: 1,
    name: 'JayBeavers',
    realName: 'Jay Beavers',
    githubUrl: 'https://github.com/JayBeavers',
    avatarUrl: 'https://avatars.githubusercontent.com/u/1682199?v=2' } ]
```

$ git shortlog -sn --no-merges 0.5.0..0.5.2-1

```
   122  John O'Nolan
    87  Paul Adam Davis
    15  Hannah Wolfe
    13  Jason Williams
    12  Felix Rieseberg
    10  Fabian Becker
     5  Matt Enlow
     3  Harry Wolff
     3  Robert Jackson
     2  David Blurton
     2  Jilles Soeters
     2  Nicola Mustone
     1  Andrej Mlinarević
     1  Jake Wright
     1  Jay Beavers
     1  Josh Vanderwillik
     1  Kirill Yakovenko
     1  Maurice Williams
     1  Pedro Teixeira
     1  Robert Rhoades
     1  Sebastian Gierlinger
     1  cobbspur
```

See the [full output from this pr](https://gist.github.com/ErisDS/8dbcd5aea191e8e6f1b1) vs [the full output from shortlog](https://gist.github.com/ErisDS/10b5c103cb396abf5296) for more details to compare.

I think this PR still yields usable results? Your about page commit is there for example.