`in` on an empty range should be false, not an error

Previously:

	julia> 1 in 1:0
	ERROR: range must be non-empty
	 in minimum at range.jl:201
	 in in at range.jl:556

All other collections (including float ranges) simply return false on an empty collection.  This (very very simple) PR fixes this and adds a few basic test cases in `test/ranges.jl`.