optimise compilation step by applying mconcat first
optimise compilation step by applying mconcat first

`writeOut` function first opened a file handle then repeatedly wrote
text. Theoretically this causes a massive overhead by invoking syscall
too often. (In practice, though, the overhead was not catastrophic since
output is buffered by default.)

Changed code to concatenate the text first in the memory and then write.

kinoru/saha,kinoru/plate,kinoru/plate,kinoru/saha