category: add "title" attribute to category anchor

Category name is used for the title.
Merge pull request #287 from kou/add-title-to-category-anchor

category: add "title" attribute to category anchor
remove guard condition for 1.8
remove coverage tool for 1.8
now json is bundled gem
fixed coverage task
remove unused require
tweak coverage in travis
remove unused option file
remove duplicate spec
remvoe const
Merge pull request #289 from tdiary/more-discontinue-1.8

More discontinue 1.8
Merge branch 'master' into gem

Conflicts:
	.travis.yml