[docs] update INSTALL.md dependencies [skip ci]

Drops mason-installed packages Boost, zlib, libpng, libuv and glfw.
Adds libtool and automake, which may be needed when mason binaries
are not available.

Drops ImageMagick, which was replaced with pixelmatch in
aaf090b &
mapbox/mapbox-gl-test-suite#50

INSTALL.md

@@ -31,14 +31,10 @@ targets.
  - Modern C++ compiler that supports `-std=c++14`
    - clang++ 3.5 or later _or_
    - g++-4.9 or later
- - [Boost headers](http://boost.org/)
- - [`zlib`](http://www.zlib.net/)
- - [`libpng`](http://www.libpng.org/pub/png/libpng.html)
- - [`libuv 0.10+`](https://github.com/joyent/libuv)
- - [`glfw 3.1+`](http://www.glfw.org/)
- - `pkg-config` (for build only)
  - Python 2.x (for build only)
- - [Imagemagick](http://www.imagemagick.org/)
+ - [`pkg-config`](https://wiki.freedesktop.org/www/Software/pkg-config/) (for build only)
+ - [`libtool`](https://www.gnu.org/software/libtool/) (for build only)
+ - [`automake`](https://www.gnu.org/software/automake/) (for build only)
 
 Depending on your operating system and target, you'll need additional
 dependencies: