Change Convert classes from internal to public

* This is for coherence reasons. If anyone can clarify what an assembly
  is we could change it back to internal. As I currently understand it,
  you need public if you want to interact with the code outside of the
  project e.g. in SparseTransform.Tests or another project that uses
  SparseTransform as a library

src/SparseTransform/Convert/ColoredDotWriter.cs

@@ -5,7 +5,7 @@ namespace SparseTransform.Convert
     /// <summary>
     /// Extends the DotWriter class to output a colored DOT graph.
     /// </summary>
-    internal class ColoredDotWriter : DotWriter
+    public class ColoredDotWriter : DotWriter
     {
         private bool textcolor;
         private string[] dictColor = new string[65];

src/SparseTransform/Convert/DotWriter.cs

@@ -6,7 +6,7 @@ namespace SparseTransform.Convert
     /// <summary>
     /// Provides an IWriter implementation that outputs an uncolored DOT graph.
     /// </summary>
-    class DotWriter : IWriter
+    public class DotWriter : IWriter
     {
         /// <summary>
         /// Transforms the <c>graph</c> to a DOT string.

src/SparseTransform/Convert/ErrorListener.cs

@@ -3,7 +3,7 @@ using Antlr4.Runtime.Misc;
 
 namespace Transform.Convert
 {
-    internal class EListener : IAntlrErrorListener<IToken>
+    public class EListener : IAntlrErrorListener<IToken>
     {
         /// <summary>
         /// specialization for parsing error handling

src/SparseTransform/Convert/IReader.cs

@@ -5,7 +5,7 @@ namespace SparseTransform.Convert
     /// <summary>
     /// Common interface for reader classes that transform a matrix input string into data structures from SparseTransform.DataStructures
     /// </summary>
-    interface IReader
+    public interface IReader
     {
         /// <summary>
         /// Transforms the <c>matrix</c> to an IGraph (respectively a Bipartite- or AdjacencyGraph)

src/SparseTransform/Convert/IWriter.cs

@@ -5,7 +5,7 @@ namespace SparseTransform.Convert
     /// <summary>
     /// Common interface for writer classes that transform a graph object to a serialized string.
     /// </summary>
-    interface IWriter
+    public interface IWriter
     {
         /// <summary>
         /// Transforms the <c>graph</c> to a string representation.

src/SparseTransform/Convert/MatrixMarketReader.cs

@@ -7,7 +7,7 @@ namespace SparseTransform.Convert
     /// <summary>
     /// Provides an IReader implementation to read a MatrixMarket string.
     /// </summary>
-    internal class MatrixMarketReader : IReader
+    public class MatrixMarketReader : IReader
     {
         public IGraph ReadGraph(string matrix)
         {

src/SparseTransform/Convert/MatrixMarketWriter.cs

@@ -6,7 +6,7 @@ namespace SparseTransform.Convert
     /// Provides an IWriter implementation that outputs a MatrixMarket string.
     /// Supports output of both the seed matrix and compressed matrix.
     /// </summary>
-    class MatrixMarketWriter : IWriter
+    public class MatrixMarketWriter : IWriter
     {
         /// <summary>
         /// If true, write (only) the seed matrix

src/SparseTransform/Convert/VisitorHeader.cs

@@ -3,7 +3,7 @@ using SparseTransform.Convert;
 
 namespace Transform.Convert
 {
-    internal class VisitorHeader : MMFHeaderBaseVisitor<bool>
+    public class VisitorHeader : MMFHeaderBaseVisitor<bool>
     {