Updated requirements.txt

chardet-1.0.1 updated to chardet-2.1.1
pyasn1-0.1.3 updated to pyasn1-0.1.7
py-1.4.9 updated to py-1.4.15 
requests-0.13.1 updated to requests-1.2.3
pytest-2.2.4 updated to pytest-2.3.5
oauthlib-0.1.3 updated to oauthlib-0.5.1