Funding for this research was provided by:
United States Agency for International Development (SOL-621-14-000015)
Received: 26 November 2017
Accepted: 12 March 2018
First Online: 20 March 2018
: The authors declare that they have no competing interests.
: Not applicable.
: Not applicable
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.