Cannot validate events, missing `check_file` function
I can't validate events, because `check_file` function is missing.

```
Environment:


Request Method: GET
Request URL: http://127.0.0.1:8000/workshops/event/2012-02-20-itcp/validate

Django Version: 1.7.1
Python Version: 2.7.9
Installed Applications:
('django.contrib.admin',
 'django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.messages',
 'django.contrib.staticfiles',
 'workshops')
Installed Middleware:
('django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.common.CommonMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.auth.middleware.SessionAuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware',
 'django.middleware.clickjacking.XFrameOptionsMiddleware')


Traceback:
File "/home/piotr/workspace/anaconda/envs/amy/lib/python2.7/site-packages/django/core/handlers/base.py" in get_response
  111.                     response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/home/piotr/workspace/amy/workshops/views.py" in validate_event
  287.             valid, error_messages = check_file(page_url, response.text)

Exception Type: NameError at /workshops/event/2012-02-20-itcp/validate
Exception Value: global name 'check_file' is not defined
```

diff --git a/workshops/views.py b/workshops/views.py
index d5ccd8fe..f0d3ecd1 100644
--- a/workshops/views.py
+++ b/workshops/views.py
@@ -15,6 +15,8 @@ from workshops.models import Site, Airport, Event, Person, Task, Cohort, Skill,
 from workshops.forms import SearchForm, InstructorsForm, PersonBulkAddForm
 from workshops.util import earth_distance
 
+from workshops.check import check_file
+
 from workshops.models import \\
     Airport, \\
     Award, \\
['workshops/views.py']