fix around help message

An error occured when exec rake task.
This is message then.

```
mkdir ./bin
mkdir ./.tmp/
cp ./src/dict ./.tmp/dict.rb
/usr/local/bin/macrubyc -o ./bin/dict ./.tmp/dict.rb
./.tmp/dict.rb:34: syntax error, unexpected ':', expecting keyword_then or ',' or ';' or '\n'
./.tmp/dict.rb:41: syntax error, unexpected keyword_else, expecting keyword_end
./.tmp/dict.rb:45: syntax error, unexpected keyword_end, expecting $end
Error when executing ` arch -x86_64 /Library/Frameworks/MacRuby.framework/Versions/0.12/usr/bin/macruby  --emit-llvm "/var/folders/4r/jjx2r3gd0yl5ppyygxm773rr0000gn/T/dictx86_64-1585.bc" MREP_FF581DB8BD2C407D81D517B649FDE084 "./.tmp/dict.rb"'
rake aborted!
Command failed with status (1): [/usr/local/bin/macrubyc -o ./bin/dict ./.t...]
/Users/kitak/tools-osx/Rakefile:27:in `block in <top (required)>'
Tasks: TOP => default
(See full trace by running task with --trace)
```