Log watched file relative to cwd, rather than absolute path.

Just makes logs shorter and easier to consume:

Absolute:
```
2013-01-22T16:34:19.467Z Watching /Users/bengourley/Projects/DCPressAndJournal/source/templates/components/pages/search-page/search-page-sidebar.jade
```

Relative:
```
2013-01-22T16:45:21.051Z Watching source/templates/components/pages/search-page/search-page-sidebar.jade
```