Documentation added: interface

General musings on possible interfaces.
First attempt at an OO-interface
Switching to Text::Filter as base class

This allows for quite a lot of shared infrastructure.
Variant without Text::Filter

Using Text::Filter as a base class did not add more than could be
achieved with the as_coderef method and a separate Text::Filter
instance, while adding a dependency. Dropped for now.
Add documentation and fix regex in alphabetize

The regex in alphabetize did not contain an end-of-word requirement
at the end. This would have caused 'zyx1' to have been sorted to
'zxy1'. Instead, such combinations are left alone now; a test is
added to ensure this.
Test for the presence of filter selectors
Adds Tests to MANIFEST, adds MANIFEST.SKIP

Removed obsolete ignore.txt.
Now the manifest test passes, which was the last one outstanding.
More Documentation

Also removes the TODO labeling from t/boilerplate.t, since it is
no longer "to do".
Consolidate READMEs into Markdown version

Since Markdown is meant to be perfectly readably plain text, it makes
sense to keep only a Markdown version (github dialect). Plain text
consumers can read it just as easily.

The consolidation of the READMEs requires changes in the MANIFEST
and the boilerplate test. The README remains as a symlink.

Add a TODO file to keep track of (internal) change requests.
Runnable script for Text::Lossy

So far, without the ability to choose filters.