Pin Yarn to 1.11.1 so it works with Node4 (https://github.com/yarnpkg/yarn/pull/6409#issuecomment-429181371)
Pin Yarn to 1.11.1 so it works with Node4 (https://github.com/yarnpkg/yarn/pull/6409#issuecomment-429181371)

yuryleb/osrm-backend,bjtaylor1/osrm-backend,frodrigo/osrm-backend,Project-OSRM/osrm-backend,frodrigo/osrm-backend,frodrigo/osrm-backend,yuryleb/osrm-backend,yuryleb/osrm-backend,felixguendling/osrm-backend,felixguendling/osrm-backend,yuryleb/osrm-backend,Project-OSRM/osrm-backend,felixguendling/osrm-backend,Project-OSRM/osrm-backend,bjtaylor1/osrm-backend,bjtaylor1/osrm-backend,bjtaylor1/osrm-backend,Project-OSRM/osrm-backend,frodrigo/osrm-backend