Added OffsetArrays as hard dependency.

This will fix it for now, but I hope this can be resolved properly at a
later date, possibly when conditional depdenencies are added to Pkg.jl

See #3.

Project.toml

@@ -6,5 +6,8 @@ authors = ["Vexatos <Stuarzt@gmx.de>"]
 url = "https://github.com/Vexatos/CircularArrays.jl"
 version = "1.0.0"
 
+[deps]
+OffsetArrays = "6fe1bfb0-de20-5000-8ca7-80f57d26f881"
+
 [compat]
 julia = "1.3"

src/CircularArrays.jl

@@ -48,8 +48,7 @@ CircularArray(def::T, size) where T = CircularArray(fill(def, size))
 @inline Base.similar(arr::CircularArray, ::Type{T}, dims::Tuple{Int64,Vararg{Int64}}) where T = _similar(arr,T,dims)
 # Ambiguity resolution with a type-pirating OffsetArrays method. See OffsetArrays issue #87.
 # Ambiguity is triggered in the case similar(arr) where arr.data::OffsetArray.
-# The OffsetAxis definition is copied from OffsetArrays.
-const OffsetAxis = Union{Integer, UnitRange, Base.OneTo, Base.IdentityUnitRange, Colon}
+using OffsetArrays: OffsetAxis
 @inline Base.similar(arr::CircularArray, ::Type{T}, dims::Tuple{OffsetAxis, Vararg{OffsetAxis}}) where T = _similar(arr,T,dims)
 
 CircularVector(data::AbstractArray{T, 1}) where T = CircularVector{T}(data)