monitor file changes: add regexp file filter

[eviltik]

Currently (v1.4.2), fs.watch watch every files.

Adding something like this in config object, so reload event is broadcasted only for specific files, i.e *.html, *.js, *.jsm

"monitorChanges": {
    "enable":"true",
    "directory":"./src",
    "fileRegexp":"\\.(html|jsm?)$"
}