`ngram_merge`: order of arguments

[mekeor]

The ngram_merge --help claims to use a different order than it really does:

$ ngram_merge --help                                                  
USAGE:
    ngram_merge <OUT> [COMPONENTS]...

$ ngram_merge output input1:1 input2:2 input3:3
thread 'main' panicked at 'index out of bounds: the len is 1 but the index is 1', evolve_keyboard_layout/src/bin/ngram_merge.rs:18:36
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

$ ngram_merge input1:1 input2:2 input3:3 output
$ echo $?
0

[dariogoetz]

Good catch. I reversed the order of the arguments for better consistency in 72cc295.