Update installation instructions
Update installation instructions

Update the installation instructions for Django 1.7 in the README.

UUDigitalHumanitieslab/texcavator,UUDigitalHumanitieslab/texcavator,msassmann/texcavator,msassmann/texcavator,UUDigitalHumanitieslab/texcavator,msassmann/texcavator,msassmann/texcavator