Use the config_file attribute to find .jscs.json

Currently the linter only search in the current directory for a .jscs.json file and fail to lint if we are working on a file in a subdirectory.

For example, here's my project:

```
my-project
 ├─┬ lib
 │ └── script.js
 └─ .jscs.json
```

With this configuration SublimeLinter-jscs cannot found the .jscs.json file.

Debug output from SublimeLinter 3 (without the fix):

```
SublimeLinter: jscs: script.js ['C:\\Users\\Yannick\\AppData\\Roaming\\npm\\jscs.cmd', '-r', 'checkstyle'] 
SublimeLinter: jscs output:
Configuration file D:\Development\my-project\lib\.jscs.json was not found. 
```

This fix add the config_file attribute to the linter to automatically define the config file path for jscs.

Debug output from SublimeLinter 3 (with the fix):

```
SublimeLinter: jscs: script.js ['C:\\Users\\Yannick\\AppData\\Roaming\\npm\\jscs.cmd', '-r', 'checkstyle', '-c', 'D:\\Development\\my-project\\.jscs.json'] 
SublimeLinter: jscs output:
<?xml version="1.0" encoding="utf-8"?>
<checkstyle version="4.3">
    <file name="c:\users\yannick\appdata\local\temp\tmpn9qtju.js">
        <error line="49" column="6" severity="error" message="Missing space after `for` keyword" source="jscs" />
        <error line="112" column="10" severity="error" message="Missing space after `catch` keyword" source="jscs" />
    </file>
</checkstyle> 
```