title: pip install - requirements.txt error
body: <pre><code>Naiches-Mini:instabot.py-master NEEcH$ pip install -r requirements.txt
  
  Collecting requests==2.12.4 (from -r requirements.txt (line 1))
  
  Using cached requests-2.12.4-py2.py3-none-any.whl
  
  Installing collected packages: requests
  
  Exception:
  
  Traceback (most recent call last):
  
  File "/Library/Python/2.7/site-packages/pip-9.0.1-py2.7.egg/pip/basecommand.py", line 215, in main status = self.run(options, args)
  
  File "/Library/Python/2.7/site-packages/pip-9.0.1-py2.7.egg/pip/commands/install.py", line 342, in run prefix=options.prefix_path,
  
  File "/Library/Python/2.7/site-packages/pip-9.0.1-py2.7.egg/pip/req/req_set.py", line 784, in install **kwargs
  
  File "/Library/Python/2.7/site-packages/pip-9.0.1-py2.7.egg/pip/req/req_install.py", line 851, in install self.move_wheel_files(self.source_dir, root=root, prefix=prefix)
  
  File "/Library/Python/2.7/site-packages/pip-9.0.1-py2.7.egg/pip/req/req_install.py", line 1064, in move_wheel_files isolated=self.isolated,
  
  File "/Library/Python/2.7/site-packages/pip-9.0.1-py2.7.egg/pip/wheel.py", line 345, in move_wheel_files clobber(source, lib_dir, True)
  
  File "/Library/Python/2.7/site-packages/pip-9.0.1-py2.7.egg/pip/wheel.py", line 316, in clobber ensure_dir(destdir)
  
  File "/Library/Python/2.7/site-packages/pip-9.0.1-py2.7.egg/pip/utils/init.py", line 83, in ensure_dir os.makedirs(path)
  
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/os.py", line 157, in makedirs mkdir(name, mode)
  
  OSError: [Errno 13] Permission denied: '/Library/Python/2.7/site-packages/requests'
  
  Naiches-Mini:instabot.py-master NEEcH$ 
  </code></pre>