Release 0.9.8 "Crowdfeeding" - Bug fixes

This is a minor release with bug fixes.

Bug fixes
=========

* isolate: Fix patterns for exponentials and logs
* doc: Fix list of currently supported models
* derivation: Allow simplification when matching against constant
* solver: Do not emit type error when guesses are constants
* expressions: Correctly substitute names in list substitutions
* menu: Fix label for `ConstantsMenu` in `MainMenu`

Improvements
============

The [INSTALL.md](../INSTALL.md) file now describes the installation
procedure.

Signed-off-by: Christophe de Dinechin <christophe@dinechin.org>