Use String#encode instead NKF
Merge pull request #190 from ayumin/kill-ruby18

Use String#encode instead NKF
.gitkeep might not be a good name for other SCM users
Fixed typo and add test
Merge pull request #192 from ayumin/typo/const_ste

Fixed typo and add test
Fix crawler to save modified items
Merge pull request #193 from iwamot/fix_crawler

Fix crawler to save modified items
Merge pull request #191 from ayumin/kill-gitkeep

.gitkkep might not be a good name for other SCM users
use eventmachine at github master

because eventmachine 1.0.3 cannot compile on ruby 2.2.0

ttps://github.com/eventmachine/eventmachine/commit/c95f1e11c2c0f0e23cd9d4ac2a9c7a75afe54710