Exclude node_modules in FileSystemFinder.

Some bower components (such as TinyMCE) require the user to use node
and npm to install build dependencies and build the static
components. This results in a node_modules, created by npm, directory
inside the bower component directory. This is a very large directory
not part of the final built static files. So ignore it.

pipeline/finders.py

@@ -97,4 +97,5 @@ class FileSystemFinder(PatternFilterMixin, FileSystemFinder):
         '*demo*',
         'Makefile*',
         'Gemfile*',
+        'node_modules',
     ]