Pip install fails in Python 2.7 for version 0.3.4

[thulasi-ram]

Changes made in commit is preventing installation of version 0.3.4 in Python 2.7: https://github.com/silentsokolov/django-admin-rangefilter/commit/718ed5ca1454139f672a52a2263ac2f185a8258d

def read_md(f):
    return open(f, 'r', encoding='utf-8').read()

pip install django-admin-rangefilter fails with TypeError: 'encoding' is an invalid keyword argument for this function

pip install django-admin-rangefilter==0.3.3 doesn't.

[silentsokolov]

Thx, fix