replace FileReader with File class; prepare for removing FileLoader

test/src/test_FileLoader.cc

@@ -7,6 +7,7 @@ TEST(FileLoaderTest, num_lines_defaults_to_0)
     EXPECT_EQ(0u, fr.num_lines());
 }
 
+#if 0
 TEST(FileLoaderTest, load_returns_false_for_nonexistent_file)
 {
     FileLoader fr;
@@ -49,3 +50,4 @@ TEST(FileLoaderTest, reads_crlf_format_file)
 //    EXPECT_EQ("Hello.", fr.get_line(0)->to_s());
 //    EXPECT_EQ("This file is in DOS line ending format.", fr.get_line(1)->to_s());
 }
+#endif