ST3: main infrastructure ported.

Fixed #20
update markdown library
Rework: lib path manager
Update CommandlineRenderer

fix #20, fix #21
Fix downloader

Refers: #20, #21
ST3: markdown renderer ported.

Fixed #22
Update python2.x docutils
Add python3.x docutils
ST2&3: Update RstRenderer

fix #23
ST3: Textile renderer ported

fix #24