simplify and fix Travis

simplify clone, add Pkg.build("Sundials")
add juliareleases to Travis matrix
juliareleases doesn't have Pkg.test
Fix printing output of ida test in runtests.jl
Merge pull request #20 from tkelman/patch-1

Simplify and fix Travis (#18).
Merge pull request #22 from acroy/runtests2

Fix output of ida test in runtests.jl
Make nvlength return Int

Fixes the following error on 32-bit systems:

ERROR: no method pointer_to_array(Ptr{Float64},(Int64,))

when calling Sundials.asarray
Merge pull request #28 from ignamv/squash

Make nvlength return Int
Create appveyor.yml
use unpacked_dir option in BinDeps

This accommodates having both 32 and 64 bit package installations on the same machine.