Add the latest GHC to travis-ci build.

[tebello-thejane]

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[tebello-thejane]

Damn! The cabal solver strikes again.

For some reason vector-0.11.0.0 and Chart-1.5.1 cannot coexist. When faced with the decision to either install vector-0.10.12.3 or Chart-1.0, cabal chooses Chart-1.0, thus breaking the build.

Also see haskell/cabal#2759

[hvr]

@tebello-thejane how can cabal know that it's supposed to choose vector-0.10.12.3 over Chart-1.0? :-)

This is a constraint-satisfaction problem with a non-unique solution, and there's no way to tell for the solver which of the solutions is to be preferred, as both are solutions are "non-optimal" (in the sense that none can use the latest versions of all packages)

[bitonic]

Thanks, I added this myself and since I also wanted to remove the previous one.