Add test codes

src/main.rs

@@ -0,0 +1,15 @@
+use std::path::PathBuf;
+
+use image::io::Reader;
+
+use waifu2x::{Convolution7, DenoiseLevel, Environment};
+
+fn main() {
+    let here = PathBuf::from(".").canonicalize().unwrap();
+    println!("here: {}", here.display());
+    let env = Environment::default().into_arc();
+    let mut model = Convolution7::new(&env, &PathBuf::from("models/upconv7"), DenoiseLevel::High).unwrap();
+    let image = Reader::open("tests/miku.png").unwrap().decode().unwrap();
+    let out = model.upscale_2x(&image).unwrap();
+    out.save("tests/miku_conv7.png").unwrap();
+}