Imported most of the old posts from WordPress.com

Thanks to
http://blog.yorkxin.org/posts/2011/11/26/import-from-wpcom-to-octopress/
Added a new post on the injectivity of stable mappings.
Updated the source with  brancch
Fixed error while running the importer script

The Chinese characters are the culprit.
Some corrections of old imported posts
Merge branch 'source' into wpcom-importer
Merge branch 'source' into wpcom-importer
Merge branch 'source' into wpcom-importer
Merge branch 'source' into wpcom-importer
Merge branch 'source' into wpcom-importer
Merge branch 'source' into wpcom-importer
Almost fixed the MathJax display problem for old posts
Merge branch 'source' into wpcom-importer
Fixed URL errors in the category list

Also fixed the incorrect display of "LaTeX" in posts imported from
WordPress.
Merge branch 'source' into wpcom-importer
Merge branch 'source' into wpcom-importer
Fixed the footnotes spacing and numbering
Importing old posts
Importing posts from WordPress.com
Fixed some errors in some of my old posts.

1. The codeblocks of those posts have been fixed.
2. The images should NOT be a part of the "mixed HTTP contents" now.