enhance README

Signed-off-by: Jean-Tiare LE BIGOT <jean-tiare.le-bigot@ovh.net>
add CONTRIBUTING guidelines

Signed-off-by: Jean-Tiare LE BIGOT <jean-tiare.le-bigot@ovh.net>
add configuration mechanisms for credentials

Signed-off-by: Jean-Tiare LE BIGOT <jean-tiare.le-bigot@ovh.net>
support kwargs notation for GET QueryStrings

Signed-off-by: Jean-Tiare LE BIGOT <jean-tiare.le-bigot@ovh.net>
add MIGRATION guide
bump version to 0.2.0