upgrade to Hexo 2.x.
Squashed 'themes/freewill/' content from commit 1096b8d

git-subtree-dir: themes/freewill
git-subtree-split: 1096b8d036de45a1a27e6bb55b77db2abe9e1b2f
Merge commit 'ea86fd61f4c035644cc595761936398080fd7605' as 'themes/freewill'
use flatly theme.
update donate page.
Translate strings in the theme.
create excerpts.
update donations.
remove light theme.
setup new release channel for Squirrel.
remove links to old release notes.
disable webfonts.