Base FileStream on eventcore.

tests/vibe.core.file.d

@@ -0,0 +1,24 @@
+/++ dub.sdl:
+	name "test"
+	dependency "vibe-core" path=".."
++/
+module test;
+
+import vibe.core.file;
+
+void main()
+{
+	auto f = openFile("test.dat", FileMode.createTrunc);
+	assert(f.size == 0);
+	f.write([1, 2, 3, 4, 5]);
+	assert(f.size == 5);
+	f.seek(0);
+	f.write([1, 2, 3, 4, 5]);
+	assert(f.size == 5);
+	f.write([6, 7, 8, 9, 10]);
+	assert(f.size == 10);
+	ubyte[5] dst;
+	f.seek(2);
+	f.read(dst);
+	assert(dst[] == [3, 4, 5, 6, 7]);
+}