A small group of activists have been walking from Mali's capital Bamako to Burkina Faso's capital Ouagadougou to express their support for a federation between the two West African states. The group are due to arrive in Ouagadougou on Tuesday where they will end their march at the Thomas Sankara memorial, a tribute to the former president and noted pan-Africanist. The prime ministers of Mali and Burkina Faso said last month they would examine the idea of creating a federation. It is not clear exactly what that would entail. The two countries share a long border and face similar challenges.…