Repository.writeFile not working

When attempting to use Repository.writeFile, this error occurs:
```
(node:8240) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'status' of undefined
at handler (C:\Program Files\nodejs\node_modules\github-api\dist\components\Requestable.js:372:40)
at processTicksAndRejections (internal/process/task_queues.js:93:5)
(Use `node --trace-warnings ...` to show where the warning was created)
(node:8240) 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: 3)
(node:8240) [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.
```

Here is the code used:
```
GitHub = require("github-api");

github = new GitHub(username, password);
repo = github.getRepo(user, repo) // actual values are "kyllta", "urlshortener"

repo.writeFile(
"main",
"test_file.txt",
"test contents",
"test commit"
);
```

Any attempts to use in HTML code (Chrome) result in this error:
```
xhr.js:177 PUT https://api.github.com/repos/kyllta/urlshortener/contents/saved_urls.json 404
  | (anonymous) | @ | xhr.js:177
-- | -- | -- | --
  | t.exports | @ | xhr.js:13
  | t.exports | @ | dispatchRequest.js:50
  | Promise.then (async) |   |  
  | n.request | @ | Axios.js:61
  | (anonymous) | @ | bind.js:9
  | value | @ | Requestable.js:183
  | (anonymous) | @ | Repository.js:787
  | Promise.then (async) |   |  
  | value | @ | Repository.js:785
  | submit | @ | (index):54
  | async function (async) |   |  
  | submit | @ | (index):32
  | onclick | @ | (index):73

```
My suspicion is incorrect headers, but I don't know much.
#577 and #520 are similar, but have different errors, and so don't seem to apply.

Bắt đầu với Repository.writeFile và handler của Requestable.js quanh dòng được báo cáo, sau đó so sánh request của trình duyệt trong Repository.js với các đối số được cung cấp và phản hồi của GitHub API. Xác minh bản sửa bằng cách tái hiện lời gọi writeFile cho repository kyllta/urlshortener mà không có status undefined hoặc phản hồi 404.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.