Be ready for the wheel binary packaging

http://pythonwheels.com/
Removed requirements files
Updated command for tests in README
Refactored function "output_default"
Cleanup
Added XPath selector to the paragraphs (closes #5)
Bump v2.1.0
Provide only license name in metadata
Documentation rewritten into RST format (closes #4)
PEP8: long line
Stop words are case insensitive
Fixed typo
Merge pull request #8 from beatinaniwa/fix_typo

Typo: lenght -> length
Respect parameter "errors" for default encoding (closes #9)
Merge pull request #2 from miso-belica/master

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