Splitting the blog directory (again)

[citrusui]

Porting the blog directory back to a submodule has a few advantages and disadvantages:

Note: core repo refers to https://github.com/citrusui/me, and blog refers to https://github.com/citrusui/blog.

Advantages

• Slightly faster git clone's
• Focused development. The core repo and blog have different goals: The former incorporates most of the functionality, and the latter provides detailed information in Markdown. Opening a pull request or issue would hopefully be directed to the core repo or the blog repo.
• Different design choices. Files directly pertaining to blog would no longer be cluttering up the core repo, and vice-versa.

Disadvantages

• Heavy reliance on _includes and _layouts. Should blog have duplicates of these folders in its own repo, or be strictly Markdown files? Would it make sense to be able to jekyll serve the standalone blog repo?
• More tests. One without the inclusion of blog, and one with blog to make sure all goes well.