Update mecab-ko-dic to 1.6.1-20140814

Updated mecab-ko-dic to 1.6.1-20140814. Also removed the caveats editing config manually and added a shell command to do it automatically instead.
How about doing this in Ruby instead?

If there should only be one occurrence of "dicdir" in the file, you could do this:

```ruby
inreplace "#{etc}/mecabrc", /dicdir = .+/, "dicdir = #{opt_prefix}"
```