* Generate meta elements from useful front matters.
Limited to the default template and specific elements.

* Rerun gofmt

* Add "keywords" and remove "language" to/from the list of meta tags.

* Add a simple positive list test for the meta tag generation.

* Move the meta tag list to a var at the begin of the file.
Seperate the Meta tags from the other front matters:
	- Don't override user settings with name `meta`
	- Cleaner Code.

* Remove the uneccessary `[:]` in the []Bytes to String casting.
@mholt was right ;)

* One minor refinement. Combining two statements.