Improve text composite

- A `Text` object should not be able to justify itself.
  All justification needs to be done by a parent.
- Apply colors and styles to part of a `Text` object
- Markup parser should return a `Text` object

src/Spectre.Console.Tests/Fixtures/AnsiConsoleFixture.cs

@@ -0,0 +1,32 @@
+using System;
+using System.IO;
+
+namespace Spectre.Console.Tests
+{
+    public sealed class AnsiConsoleFixture : IDisposable
+    {
+        private readonly StringWriter _writer;
+
+        public IAnsiConsole Console { get; }
+
+        public string Output => _writer.ToString();
+
+        public AnsiConsoleFixture(ColorSystem system, AnsiSupport ansi = AnsiSupport.Yes, int width = 80)
+        {
+            _writer = new StringWriter();
+
+            Console = new ConsoleWithWidth(
+                AnsiConsole.Create(new AnsiConsoleSettings
+                {
+                    Ansi = ansi,
+                    ColorSystem = (ColorSystemSupport)system,
+                    Out = _writer,
+                }), width);
+        }
+
+        public void Dispose()
+        {
+            _writer?.Dispose();
+        }
+    }
+}

src/Spectre.Console.Tests/Fixtures/ConsoleWithWidth.cs

@@ -0,0 +1,31 @@
+using System.Text;
+
+namespace Spectre.Console.Tests
+{
+    public sealed class ConsoleWithWidth : IAnsiConsole
+    {
+        private readonly IAnsiConsole _console;
+
+        public Capabilities Capabilities => _console.Capabilities;
+
+        public int Width { get; }
+        public int Height => _console.Height;
+
+        public Encoding Encoding => _console.Encoding;
+
+        public Styles Style { get => _console.Style; set => _console.Style = value; }
+        public Color Foreground { get => _console.Foreground; set => _console.Foreground = value; }
+        public Color Background { get => _console.Background; set => _console.Background = value; }
+
+        public ConsoleWithWidth(IAnsiConsole console, int width)
+        {
+            _console = console;
+            Width = width;
+        }
+
+        public void Write(string text)
+        {
+            _console.Write(text);
+        }
+    }
+}

src/Spectre.Console.Tests/Fixtures/PlainConsole.cs

@@ -0,0 +1,42 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+
+namespace Spectre.Console.Tests
+{
+    public sealed class PlainConsole : IAnsiConsole, IDisposable
+    {
+        public Capabilities Capabilities => throw new NotSupportedException();
+        public Encoding Encoding { get; }
+
+        public int Width { get; }
+        public int Height { get; }
+
+        public Styles Style { get; set; }
+        public Color Foreground { get; set; }
+        public Color Background { get; set; }
+
+        public StringWriter Writer { get; }
+        public string Output => Writer.ToString().TrimEnd('\n');
+        public IReadOnlyList<string> Lines => Output.Split(new char[] { '\n' });
+
+        public PlainConsole(int width = 80, int height = 9000, Encoding encoding = null)
+        {
+            Width = width;
+            Height = height;
+            Encoding = encoding ?? Encoding.UTF8;
+            Writer = new StringWriter();
+        }
+
+        public void Dispose()
+        {
+            Writer.Dispose();
+        }
+
+        public void Write(string text)
+        {
+            Writer.Write(text);
+        }
+    }
+}