Update akka 2.5.14 in master docs/build.sbt (#1447)
Update akka 2.5.14 in master docs/build.sbt (#1447)

This completes https://github.com/lagom/lagom/pull/1445 (`master`) which was merged prematurely.
TimMoore/lagom,TimMoore/lagom,TimMoore/lagom,lagom/lagom,ignasi35/lagom,TimMoore/lagom,rcavalcanti/lagom,rstento/lagom,lagom/lagom,rcavalcanti/lagom,ignasi35/lagom,lagom/lagom,rstento/lagom,rcavalcanti/lagom,rstento/lagom,ignasi35/lagom,TimMoore/lagom,ignasi35/lagom,lagom/lagom,ignasi35/lagom,rcavalcanti/lagom,rstento/lagom,rstento/lagom,lagom/lagom