Specify django_compressor version to 1.3 and higher

The d3 library requires django-compressor version 1.3 and higher

Fixes: bug #1184653

Change-Id: I4c0e4fb96b7ef2535efe1a818c884c371cbdcbc5
Avoid duplicate pep8 generation

pep8 requirements were always written twice to the
updated requirements. Simply preserve the original pep8
line, like the source code comment mentioned.

Change-Id: I6b23f756594feeea0a5dbe14c58be981501bc5a4
Merge "Avoid duplicate pep8 generation"
Merge "Specify django_compressor version to 1.3 and higher"