A general app for doing typeahead
It needs a list to choose from and a to-string
function to display and filter the list.

A buffer could be considered a slider (see slider) with
some extra attributes, besides attributes to keep track
of name, filename, dirtyness, undo information it consists
of

  * A slider
  * A highlighter function
  * A keymap

The slider is used to keep track of the text, the highlighter
function is used by the view to apply highlight and the
keymap is used to decide which function a keypress should
be mapped to.

On runtime the highlighter function and the keymap can be
replaced.

The buffer structure is immutable, so every operation that
changes the buffer will return a new one.

The editor is the central point of Liquid.
Most of the data is immutable, but the editor has
a ref, also called editor. It contains the state of
the editor.

Most actions on the editor will replace content of this state
with a transformed content.

For example:

  When (forward-char 1) is called, the current buffer will be
  replaced with a new buffer, where the cursor is moved one char
  ahead.

The slider is a basic construction resembling the most
fundamental actions of a text edtior.

The slider is immutable, so every slider function in this
namespace will take a slider as input together with some
parameters and evaluate to a new slider.

By having the slider as first parameter a series of actions
can be performed by using the threading operator "->",
like:

(->
  sl
  (end-of-line)
  (forward-char 3))

Some of the basic operations are:

* Moving cursor
* Inserting and removing content
* Setting marks and moving cursor to marks
* Marking regions

The sliderutil contains more slider related functions,
which are more complex and usually composed of the basic
functions in this file.

A namespace for shell like utils
in clojure style.