Fix path separator issue on Windows vs Linux

[dstj]

On Windows, the hardcoded / directory separator caused the following error. Using path.sep fixes the issue.

[17:43:42] Using gulpfile D:\Dev\testing\gulp-mock-server\gulpfile.js
[17:43:42] Starting 'mock'...
[17:43:42] Webserver started at http://localhost:8090
TypeError: Cannot call method 'split' of undefined
    at D:\Dev\testing\gulp-mock-server\node_modules\gulp-mock-server\src\mock.js:16:38
    at Array.map (native)
    at module.exports (D:\Dev\testing\gulp-mock-server\node_modules\gulp-mock-server\src\mock.js:16:6)
    at call (D:\Dev\testing\gulp-mock-server\node_modules\gulp-mock-server\node_modules\connect\index.js:239:7)
    at next (D:\Dev\testing\gulp-mock-server\node_modules\gulp-mock-server\node_modules\connect\index.js:183:5)
    at D:\Dev\testing\gulp-mock-server\node_modules\gulp-mock-server\node_modules\connect-query\index.js:8:5
    at call (D:\Dev\testing\gulp-mock-server\node_modules\gulp-mock-server\node_modules\connect\index.js:239:7)
    at next (D:\Dev\testing\gulp-mock-server\node_modules\gulp-mock-server\node_modules\connect\index.js:183:5)
    at jsonParser (D:\Dev\testing\gulp-mock-server\node_modules\gulp-mock-server\node_modules\body-parser\lib\types\json.js:100:40)
    at call (D:\Dev\testing\gulp-mock-server\node_modules\gulp-mock-server\node_modules\connect\index.js:239:7)
TypeError: Cannot call method 'split' of undefined
    at D:\Dev\testing\gulp-mock-server\node_modules\gulp-mock-server\src\mock.js:16:38
    at Array.map (native)
    at module.exports (D:\Dev\testing\gulp-mock-server\node_modules\gulp-mock-server\src\mock.js:16:6)
    at call (D:\Dev\testing\gulp-mock-server\node_modules\gulp-mock-server\node_modules\connect\index.js:239:7)
    at next (D:\Dev\testing\gulp-mock-server\node_modules\gulp-mock-server\node_modules\connect\index.js:183:5)
    at D:\Dev\testing\gulp-mock-server\node_modules\gulp-mock-server\node_modules\connect-query\index.js:8:5
    at call (D:\Dev\testing\gulp-mock-server\node_modules\gulp-mock-server\node_modules\connect\index.js:239:7)
    at next (D:\Dev\testing\gulp-mock-server\node_modules\gulp-mock-server\node_modules\connect\index.js:183:5)
    at jsonParser (D:\Dev\testing\gulp-mock-server\node_modules\gulp-mock-server\node_modules\body-parser\lib\types\json.js:100:40)
    at call (D:\Dev\testing\gulp-mock-server\node_modules\gulp-mock-server\node_modules\connect\index.js:239:7)

[dstj]

No longer crashes on Windows, but does not support multi-level directory...

[dstj]

Directory nesting on Windows is fixed. Pull request has been updated.