Remove imports which are no longer available in v1.0. (#43)

Apparently they were not used anyway.

Author: tpapp

src/Contour.jl

@@ -14,7 +14,7 @@ export
     lines,
     coordinates
 
-import Base: push!, start, next, done, length, eltype, show
+import Base: push!, length, eltype, show
 
 struct Curve2{T}
     vertices::Vector{SVector{2,T}}