Add new permalink param: post_title

[nt3rp]

To avoid breaking any existing setups, create a new param which represents the title of a post.

Also, addresses #881 (as far as the problem I described there)

[nt3rp]

I think that the proper fix would be to change this line, to this:

title: util.slugize(data.title, {transform: 1}),

... but that could break existing setups 😞

[coveralls]

Coverage remained the same at 95.41% when pulling 054b2b4 on nt3rp:permalink_postname into eff1429 on hexojs:master.

[tommy351]

What's different between slug and post_title?

[nt3rp]

From my understanding, slug in the permalink is equivalent to new_post_name minus the file extension. post_title is the slugized version of the actual post title.

The problem mostly arises in cases like #881.

[tommy351]

I see.