sample: Add output file option

Some dependencies erroneously print diagnostic
messages to stdout, mixing them with sampling result.

-file option allows workaround this

Author: vi

sample.lua

@@ -13,6 +13,7 @@ cmd:option('-temperature', 1)
 cmd:option('-gpu', 0)
 cmd:option('-gpu_backend', 'cuda')
 cmd:option('-verbose', 0)
+cmd:option('-output', '-')
 local opt = cmd:parse(arg)
 
 
@@ -39,4 +40,11 @@ if opt.verbose == 1 then print(msg) end
 model:evaluate()
 
 local sample = model:sample(opt)
-print(sample)
+if opt.output == "-" then
+    print(sample)
+else
+    require 'io'
+    local outfile = io.open(opt.output, "w")
+    outfile:write(sample)
+    outfile:close()
+end