Added package_available(), available_version() for yum
Added package_available(), available_version() for yum

tkelman/BinDeps.jl,rened/BinDeps.jl,tlycken/BinDeps.jl,andrewcooke/BinDeps.jl,chezou/BinDeps.jl,JuliaPackageMirrors/BinDeps.jl