Replacing request.el with our own fork.

The primary change is that we now get proper JSON response data in error
responses. This is critical for properly interacting with YCMD.
Or better:
```
(expand-file-name "third-party" (file-name-directory (or load-file-name (buffer-file-name))))
```

to allow to evaluate the buffer.
`load-file-name` is nil when evaluating buffer and `(buffer-file-name)` is nil when loading.