Enhance user experience

I fixed ImportError when package install. 
And I made print result method for module.

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Traceback (most recent call last):
  File "setup.py", line 7, in <module>
    from hog import VERSION, PROJECT
  File "~/hog/hog/__init__.py", line 13, in <module>
    **from .hog import run**                                                 
  File "~/hog/hog/hog.py", line 20, in <module>
    import requests
ImportError: No module named requests

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import hog
r = hog.run('http://some.where', concurrency=100, requests=500, timeout=10)
hog.print_result(r)