Tips for README improvement

[ReekenX]

Hi there!

Your module is awesome! Used it couple of times already.

Still, I see couple of improvements, like:

1. Description part "you set in a text file" should be bolded. When you want to try module fast (just pip install and copy-paste configuration) you still will end up reading your whole readme file and wondering "why it still not working". Because you need to create a file with list of user agents.

2. I was able to find only small amount of user agents lists already built, like: https://github.com/cvandeplas/pystemon/blob/master/user-agents.txt So maybe this can be used as helpful tip in Readme? I understand "single responsibility priciple" - your app does one thing and does it right, but without actual file nobody can use your application.

[super1-chen]

guys, I think if you add a user-agent file example in the repo, should be better