Wrapper for ExaML phylogenetic inference added

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Hi, I went through my repositories and noticed I had never added the ExaML wrapper that I wrote at the BOSC codefest!

The ExaML wrapper looks much like the already existing one for RAxML. Additionally, there is parallel support given by the setters mpirun and cores in which one can specify mpirun location and the number of processors used for the inference.

Hope this can be made part of bioperl, Best,

Hannes

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Closed and reopened to fix travis built.