Add new test.

Based on #131

tests/read_file_with_seek.rs

@@ -0,0 +1,26 @@
+mod utils;
+
+static FILE_TO_READ: &str = "64MB.DAT";
+
+#[test]
+fn read_file_with_seek() {
+    let time_source = utils::make_time_source();
+    let disk = utils::make_block_device(utils::DISK_SOURCE).unwrap();
+    let mut volume_mgr = embedded_sdmmc::VolumeManager::new(disk, time_source);
+
+    let mut volume = volume_mgr
+        .open_volume(embedded_sdmmc::VolumeIdx(0))
+        .unwrap();
+    let mut root_dir = volume.open_root_dir().unwrap();
+    println!("\nReading file {}...", FILE_TO_READ);
+    let mut f = root_dir
+        .open_file_in_dir(FILE_TO_READ, embedded_sdmmc::Mode::ReadOnly)
+        .unwrap();
+    f.seek_from_start(0x2c).unwrap();
+    while f.offset() < 1000000 {
+        let mut buffer = [0u8; 2048];
+        f.read(&mut buffer).unwrap();
+        f.seek_from_current(-1024).unwrap();
+    }
+    println!("Done!");
+}