Initial work

Create Reader
Pulled back in Inode decoding and superblock
New Data and Metadata readers
Added getting of id, fragment, and export table data lazily
Added README to squashfs/squashfs

internal/toreader/toreader.go

@@ -0,0 +1,21 @@
+package toreader
+
+import "io"
+
+type Reader struct {
+	r      io.ReaderAt
+	offset int64
+}
+
+func NewReader(r io.ReaderAt, start int64) *Reader {
+	return &Reader{
+		r:      r,
+		offset: start,
+	}
+}
+
+func (r *Reader) Read(b []byte) (int, error) {
+	n, err := r.r.ReadAt(b, r.offset)
+	r.offset += int64(n)
+	return n, err
+}