Drop support for Julia 0.5

v0.8.0

Update REQUIRE

Factor out reverse functions into `IntervalContractors.jl`

Reverse (inverse) functions / contractors now live in the IntervalContractors.jl package, and many more
functions are available (sin, cos, exp, abs, etc.)

Bump minimum Julia version to 0.5; use IntervalArithmetic instead of ValidatedNumerics

See https://github.com/JuliaIntervals/IntervalConstraintProgramming.jl/blob/master/NEWS.md for details.

API change: Contractors now have dimensions as type parameters

See NEWS.md for more detail.

Local variables and functions

Add local variables and functions in constraints.

Update to a version that is working

v0.2.0 was broken.
Minor tag since API change (setinverse -> pave).