Updated requirements.txt

execnet-1.0.9 updated to execnet-1.1
chardet-1.0.1 updated to chardet-2.1.1
py-1.4.8 updated to py-1.4.15
pytest-2.2.4 updated to pytest-2.3.5
BeautifulSoup-3.2.0 updated to BeautifulSoup-3.2.1