Add support for TAG feeds
Fix typo in makefile output
Fix mis-tagging/-categorization of posts

The bug would manifest itself whe you first published a post "X" and
then published a post "XY" (i.e. where the *first* post had a normalized
filename that was a subset of a later posts normalized filename).

In this case, any tag, and the category applied to the *first* post,
would generate a tag/category index listing also the second post, when
the second post wasn't intended to be tagged/categorized with that.

Example:

blah draft post "Test #1"
blah publish drafts/post/test_1/
<categorize as "Just A Test">
<tag with "Foo">

live/<date>/test_1/index.html will correctly enumerate category "Just A
Test" and tag "Foo"

live/tag/foo/index.html will correctly display a link to
live/<date>/test_1/index.html

live/category/just_a_test/index.html will correctly display a link to
live/<date>/test_1/index.html

blah draft post "Test #1 - Continued"
blah publish drafts/post/test_1_continued"
<categorize as "Another Test">
<tag with "Bar">

live/<date>/test_1_continued/index.html will correctly enumerate
category "Another Test" and tag "Bar"

live/tag/foo/index.html will correctly display a link to
live/<date>/test_1/index.html

live/tag/foo/index.html will *INCORRECTLY* display a link to
live/<date>/test_1_continued/index.html

live/tag/bar/index.html will correctly display a link to
live/<date>/test_1_continued/index.html

live/category/just_a_test/index.html will correctly display a link to
live/<date>/test_1/index.html

live/category/just_a_test/index.html will *INCORRECTLY* display a link to
live/<date>/test_1_continued/index.html

live/category/another_test/index.html will correctly display a link to
live/<date>/test_1_continued/index.html