check the real path for a watched parent

This change creates fs instances for symlinks that link out to a file not in an already watched directory which is the parent of the symlink. Specifically this fixes watching files that have been npm link'd.

There might be a more efficient answer, that creates an fs instance for the symlinked directory, but as far as i could tell the only reason, my parent directory is currently being watched is because karma-browserify specifically includes the package.json as a watched file. That is, it doesn't seem to be something chokidar is doing intentionally.
Resolve symlinks with realpath instead of readlink

gh-31
Prevent redundant realpath call
Merge pull request #196 from scamden/patch-1

check the real path for a watched parent
Remove redundant sysPath.resolve
Release 0.12.2
Include special files in directory scans

Resolves gh-192
Release 0.12.3
Fix ready event when symlink links to ignored path
Fix cwd vs watched path confusion

Resolves gh-195
Release 0.12.4
test for watching symlinks to files outside an already watched dir