prevent requirements.txt from being installed to /usr

MANIFEST.in

@@ -4,6 +4,8 @@ include electrum.conf.sample
 include electrum.desktop
 include *.py
 include electrum
+include contrib/requirements/requirements.txt
+include contrib/requirements/requirements-hw.txt
 recursive-include lib *.py
 recursive-include gui *.py
 recursive-include plugins *.py

setup.py

@@ -20,7 +20,7 @@ version = imp.load_source('version', 'lib/version.py')
 if sys.version_info[:3] < (3, 4, 0):
     sys.exit("Error: Electrum requires Python version >= 3.4.0...")
 
-data_files = ['contrib/requirements/' + r for r in ['requirements.txt', 'requirements-hw.txt']]
+data_files = []
 
 if platform.system() in ['Linux', 'FreeBSD', 'DragonFly']:
     parser = argparse.ArgumentParser()