Added ghc dependency in travis config.
Added ghc dependency in travis config.

charleso/intellij-haskforce,carymrobbins/intellij-haskforce,begray/intellij-haskforce,KasperJanssens/intellij-haskforce,charleso/intellij-haskforce,carymrobbins/intellij-haskforce,begray/intellij-haskforce,charleso/intellij-haskforce,KasperJanssens/intellij-haskforce,begray/intellij-haskforce,carymrobbins/intellij-haskforce