Fix for user agents with leading or enclosing quotes

In examining my HTTP logs, I found user agents that were double-quoted and that had a single leading quote:

````
"Mozilla/5.0 (X11; Linux x86_64; rv:9.0) Gecko/20100101 Firefox/9.0"
'Mozilla/5.0
````

This pull request changes the regex match to ignore quotes and adds RSpec tests for these cases.

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733 examples, 0 failures
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