Use text mode to read files in setup.py

This fixes python3 compatibility which will otherwise read bytes objects.
While the fix is not ideal (the encoding is implicit and depends on
current system locale) it is a good compromise for python3 support

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@canonical.com>
Use use_2to3 to support python3

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@canonical.com>