Follow markdown style guide for filename generation

http://www.cirosantilli.com/markdown-style-guide/

Prefer to base the file name on the top-header level:
-  replace upper case letters with lower case
-   strip articles the, a, an from the start
-   replace punctuation and white space characters by hyphens
-   replace consecutive hyphens by a single hyphen
-   strip surrounding hyphens
