docs/phonemes.md: restructure the suprasegmental features.

docs/phoneme_model.md

 - [Consonant Release](#consonant-release)
 - [Tongue Root](#tongue-root)
 - [Fortis and Lenis](#fortis-and-lenis)
+- [Stress](#stress)
+- [Length](#length)
+- [Rhythm](#rhythm)
+- [Intonation](#intonation)
+- [Tone Stepping](#tone-stepping)
+- [Tones](#tones)
 - [References](#references)
 
 ----------
 | `fts`   | fortis |
 | `lns`   | lenis  |
 
+## Stress
+
+| Feature | Name             |
+|---------|------------------|
+| `st1`   | primary stress   |
+| `st2`   | secondary stress |
+| `st3`   | extra stress     |
+
+## Length
+
+| Feature | Name            |
+|---------|-----------------|
+| `est`   | extra short     |
+| `hlg`   | half-long       |
+| `lng`   | long            |
+
+## Rhythm
+
+| Feature | Name              |
+|---------|-------------------|
+| `sbr`   | syllable break    |
+| `lnk`   | linked (no break) |
+
+## Intonation
+
+| Feature | Name                     |
+|---------|--------------------------|
+| `fbr`   | minor (foot) break       |
+| `ibr`   | major (intonation) break |
+| `glr`   | global rise              |
+| `glf`   | global fall              |
+
+## Tone Stepping
+
+| Feature | Name        |
+|---------|-------------|
+| `ust`   | upstep      |
+| `dst`   | downstep    |
+
+## Tones
+
+Tones are defined using the following 3 properties:
+
+	tone_start  <value>
+	tone_middle <value>
+	tone_end    <value>
+
+The `<value>` field for these properties is a number with one of the following
+values:
+
+| Tone               | `<value>` |
+|--------------------|-----------|
+| extra high (top)   | `5`       |
+| high               | `4`       |
+| mid                | `3`       |
+| low                | `2`       |
+| extra low (bottom) | `1`       |
+
+A *level* tone can be specified by just using the `tone_start` value. A *raising*
+or *falling* tone can be specified using the `tone_start` and `tone_end` values.
+A *raising-falling* (*peaking*) or *falling-raising* (*dipping*) tone can be
+specified using all three values.
+
 ## References
 
 1. <a name="ref1"></a> Kirshenbaum, Evan,

docs/phonemes.md

   - [Co-articulation](#co-articulation)
   - [Tongue Root](#tongue-root)
   - [Fortis and Lenis](#fortis-and-lenis)
-  - [Suprasegmentals](#suprasegmentals)
-    - [Stress](#stress)
-    - [Length](#length)
-    - [Rhythm](#rhythm)
-    - [Intonation](#intonation)
+- [Suprasegmentals](#suprasegmentals)
+  - [Stress](#stress)
+  - [Length](#length)
+  - [Rhythm](#rhythm)
+  - [Intonation](#intonation)
   - [Tone Stepping](#tone-stepping)
-- [Properties](#properties)
   - [Tones](#tones)
 - [References](#references)
 
 the Jawoyn, Ojibwe, and Zurich German languages<sup>\[<a href="#ref8">8</a>\]</sup>),
 the [length](#length) suprasegmentals are used instead.
 
-### Suprasegmentals
+## Suprasegmentals
 
-#### Stress
+### Stress
 
 | Feature | Symbol | Name             |
 |---------|--------|------------------|
 | `st2`   | ˌ◌     | secondary stress |
 | `st3`   | ˈˈ◌    | extra stress     |
 
-#### Length
+### Length
 
 | Feature | Symbol | Name            |
 |---------|--------|-----------------|
 | `hlg`   | ◌ˑ     | half-long       |
 | `lng`   | ◌ː     | long            |
 
-#### Rhythm
+### Rhythm
 
 | Feature | Symbol | Name              |
 |---------|--------|-------------------|
 | `sbr`   | ◌.◌    | syllable break    |
 | `lnk`   | ◌‿◌    | linked (no break) |
 
-#### Intonation
+### Intonation
 
 | Feature | Symbol | Name                     |
 |---------|--------|--------------------------|
 | `glr`   | ↗      | global rise              |
 | `glf`   | ↘      | global fall              |
 
-#### Tone Stepping
+### Tone Stepping
 
 | Feature | Symbol | Name        |
 |---------|--------|-------------|
 | `ust`   | ꜛ◌     | upstep      |
 | `dst`   | ꜜ◌     | downstep    |
 
-## Properties
-
 ### Tones
 
 Tones are defined using the following 3 properties: