Update waifu2x.lua, default model=cunet/art

waifu2x.lua

@@ -254,11 +254,11 @@ local function waifu2x()
    cmd:option("-scale", 2, 'scale factor')
    cmd:option("-o", "(auto)", 'path to output file')
    cmd:option("-depth", 8, 'bit-depth of the output image (8|16)')
-   cmd:option("-model_dir", "./models/upconv_7/art", 'path to model directory')
+   cmd:option("-model_dir", "./models/cunet/art", 'path to model directory')
    cmd:option("-name", "user", 'model name for user method')
    cmd:option("-m", "noise_scale", 'method (noise|scale|noise_scale|user)')
    cmd:option("-method", "", 'same as -m')
-   cmd:option("-noise_level", 1, '(1|2|3)')
+   cmd:option("-noise_level", 1, '(0|1|2|3)')
    cmd:option("-crop_size", 256, 'patch size per process')
    cmd:option("-batch_size", 1, 'batch_size')
    cmd:option("-resume", 0, "skip existing files (0|1)")