Subject: Buggy code to import GitHub gist.

Description:

1. Buggy code to import GitHub gist.

2. CodeMirror height restore to fixed(#FIXME). It should auto resize
based on content(height-wise) but limit 'max-height'.
Subject: BUGFIX: Check for URL(and load the code snippet) else load
code from code field.

Description:

1. Validation for URL and code fields in forms.py
2. Example GitHub Gist URL changed.
Subject: BUG: No url 404 warning.

Description:
Subject: Search code.

Description:
Subject: Search by 'contains' instead of 'startswith'.

Description:
Subject: BUGFIX: issue #8