[WIP] Interfacing Arb with CSymPy

ARB depends on (source- http://fredrikj.net/arb/setup.html#dependencies) :
* MPIR/GMP (we already have GMP so this is taken care of)
* MPFR
* FLINT

So in Travis we will have to explicitly install the other 2 libraries before installing ARB
You can install mpfr in Ubuntu using `apt-get install libmpfr-dev`, that will be much faster.