Implement CsvFieldIndexer.

Fixes #2

CsvLib/BufferedTextReader.cs

@@ -0,0 +1,54 @@
+using System;
+using System.IO;
+using System.Text;
+
+namespace CsvLib
+{
+    public class BufferedTextReader : TextReader
+    {
+        private readonly TextReader _baseReader;
+        private int _position;
+        private readonly StringBuilder _sbBuffer = new StringBuilder();
+
+        public BufferedTextReader(TextReader baseReader)
+        {
+            _baseReader = baseReader;
+        }
+
+        public override int Read()
+        {
+            _position++;
+            int read = _baseReader.Read();
+            if (read != -1)
+            {
+                _sbBuffer.Append((char)read);
+            }
+            return read;
+        }
+
+        public override int Read(char[] buffer, int index, int count)
+        {
+            throw new NotImplementedException("Read buffered method on BufferedTextReader");
+        }
+
+        public override int Peek()
+        {
+            return _baseReader.Peek();
+        }
+
+        public int Position
+        {
+            get { return _position; }
+        }
+
+        public string GetBuffer()
+        {
+            return _sbBuffer.ToString();
+        }
+
+        public void CleanBuffer()
+        {
+            _sbBuffer.Clear();
+        }
+    }
+}