add `fab components`

installs components with bower

IPython/frontend/html/notebook/fabfile.py

@@ -1,26 +1,30 b''
 """ fabfile to prepare the notebook """
 
 from fabric.api import local,lcd
 from fabric.utils import abort
 import os
 
 static_dir = 'static'
 components_dir = os.path.join(static_dir,'components')
 
 def test_component(name):
     if not os.path.exists(os.path.join(components_dir,name)):
-        abort('cannot continue without component {}.'.format(name))
+        components()
 
+def components():
+    """install components with bower"""
+    with lcd(static_dir):
+        local('bower install')
 
 def css(minify=True):
     """generate the css from less files"""
     test_component('bootstrap')
     test_component('less.js')
-    if minify not in ['True','False',True,False]:
-        abort('need to get Boolean')
+    if minify not in ['True', 'False', True, False]:
+        abort('minify must be Boolean')
     minify = (minify in ['True',True])
 
     min_flag= '-x' if minify is True else ''
     with lcd(static_dir):
         local('lessc {min_flag} less/style.less css/style.min.css'.format(min_flag=min_flag))