docs/install: Update python dependency section

Note that meson requires python 3, scons requires python 2, and
autotools works with either.

Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Eric Engeström <eric@engestrom.ch>
diff --git a/docs/install.html b/docs/install.html
index d010eed..b6a75ba 100644
--- a/docs/install.html
+++ b/docs/install.html
@@ -74,7 +74,9 @@
 
 <ul>
 <li><a href="https://www.python.org/">Python</a> - Python is required.
-Version 2.7 or later should work.
+When building with scons 2.7 is required.
+When building with meson 3.5 or newer is required.
+When building with autotools 2.7, or 3.5 or later are required.
 </li>
 <li><a href="http://www.makotemplates.org/">Python Mako module</a> -
 Python Mako module is required. Version 0.8.0 or later should work.