Fix namespace
Modify HaikMarkdown option.

empty_element_suffix = "" #empty text
Add HaikMarkdown::doHaikLinks.

add below rules:
- [[PageName]] -> Hypertext anchor tag to the page
- [[Alias>PageName]] -> Hypertext anchor tag to the page with alias text
- [[#hash]] -> Hypertext anchor tag to the hash within current page

add test:
- doHaikLinks
- doInlinePlugins (prototype)
Delete a test file with invalid filename