Code restructuring, assigning proper subsystems to each

- Drivers contain
    * donut/*
    * file/*
    * memory/*

 - Storage format contains
    * donut/*
      - GetObject() --> renamed to GetObjectReader()
      - Deleted stale objectwriter.go, renamed donutwriter.go to object_writer.go

Simplifying, and documenting codebase further

pkg/drivers/donut/donut_test.go

@@ -0,0 +1,54 @@
+/*
+ * Minimalist Object Storage, (C) 2015 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package donut
+
+import (
+	"io/ioutil"
+	"os"
+	"testing"
+
+	"github.com/minio-io/minio/pkg/drivers"
+
+	. "gopkg.in/check.v1"
+)
+
+func Test(t *testing.T) { TestingT(t) }
+
+type MySuite struct{}
+
+var _ = Suite(&MySuite{})
+
+func (s *MySuite) TestAPISuite(c *C) {
+	//	c.Skip("Not Implemented")
+	var storageList []string
+	create := func() drivers.Driver {
+		path, err := ioutil.TempDir(os.TempDir(), "minio-fs-")
+		c.Check(err, IsNil)
+		storageList = append(storageList, path)
+		_, _, store := Start(path) // TODO Make InMemory driver
+		return store
+	}
+	drivers.APITestSuite(c, create)
+	removeRoots(c, storageList)
+}
+
+func removeRoots(c *C, roots []string) {
+	for _, root := range roots {
+		err := os.RemoveAll(root)
+		c.Check(err, IsNil)
+	}
+}