drop the remnants of v0.6 compatibility

REQUIRE

@@ -1,5 +1,4 @@
 julia 0.7
-Compat 0.69
 RecipesBase 0.2.3
 PlotUtils 0.4.1
 PlotThemes 0.1.3

src/Plots.jl

@@ -13,7 +13,6 @@ using Base.Meta
 @reexport using PlotUtils
 @reexport using PlotThemes
 
-if VERSION >= v"0.7-"
 import Dates
 using Dates: Date, DateTime
 using Printf: @printf, @sprintf
@@ -21,15 +20,8 @@ if VERSION >= v"0.7-"
 using Base64: base64encode
 using Base.Sys: isapple, islinux, iswindows, isbsd
 import Pkg
+using LinearAlgebra: Transpose
 const euler_e = Base.MathConstants.e
-else
-    using Compat
-    using Compat.Sys: isapple, islinux, iswindows, isbsd
-    import Compat: maximum
-    maximum(arg::Tuple) = Base.maximum(arg)
-    using Base.REPL: REPLDisplay
-    const euler_e = Base.e
-end
 
 import Showoff
 import StatsBase

src/backends.jl

@@ -14,7 +14,6 @@ backend_name() = CURRENT_BACKEND.sym
 _backend_instance(sym::Symbol) = haskey(_backendType, sym) ? _backendType[sym]() : error("Unsupported backend $sym")
 
 # kludge while waiting for Pkg alternatives
-if VERSION >= v"0.7-"
 function _findmod(f::Symbol)
     for (u,v) in Base.loaded_modules
         (Symbol(v) == f) && return u
@@ -26,11 +25,6 @@ function topimport(modname)
     u = _findmod(modname)
     @eval $modname = Base.loaded_modules[$u]
 end
-else
-    function myimport(modname)
-        @eval import $modname
-    end
-end
 # end kludge
 
 macro init_backend(s)

src/examples.jl

@@ -413,7 +413,7 @@ attribute. The default framestyle is `:axes`.
     scatter(fill(randn(10), 6), fill(randn(10), 6),
         framestyle = [:box :semi :origin :zerolines :grid :none],
         title = [":box" ":semi" ":origin" ":zerolines" ":grid" ":none"],
-        color = RowVector(1:6), layout = 6, label = "", markerstrokewidth = 0,
+        color = Transpose(1:6), layout = 6, label = "", markerstrokewidth = 0,
         ticks = -2:2)
     end)]
 ),