Port to netstandard.

Nit fixes.
Fixed e2e tests.
Added MIT license.

SystemExtensions.NetStandard/Collections/IQueue.cs

@@ -0,0 +1,39 @@
+namespace System.Collections.Generic
+{
+    /// <summary>
+    /// Interface for queue implementations.
+    /// </summary>
+    /// <typeparam name="T">Provided type.</typeparam>
+    public interface IQueue<T> : IEnumerable<T>
+    {
+        /// <summary>
+        /// Returns the number of items in the queue.
+        /// </summary>
+        int Count { get; }
+        /// <summary>
+        /// Inserts item into the queue.
+        /// </summary>
+        /// <param name="item">Item to be inserted.</param>
+        void Enqueue(T item);
+        /// <summary>
+        /// Remove the first item in the queue.
+        /// </summary>
+        /// <returns>First item in the queue.</returns>
+        T Dequeue();
+        /// <summary>
+        /// Looks up the first item from the queue without removing it.
+        /// </summary>
+        /// <returns>First item from the queue.</returns>
+        T Peek();
+        /// <summary>
+        /// Clears the contents of the queue.
+        /// </summary>
+        void Clear();
+        /// <summary>
+        /// Checks if queue contains an item.
+        /// </summary>
+        /// <param name="item">Item to be checked.</param>
+        /// <returns>True if queue contains provided item. False otherwise.</returns>
+        bool Contains(T item);
+    }
+}