Start an FAQ and answer it with a new install section

sites/www/faq.rst

@@ -0,0 +1,9 @@
+===================================
+Frequently Asked/Answered Questions
+===================================
+
+Which version should I use? I see multiple active releases.
+===========================================================
+
+Please see :ref:`the installation docs <release-lines>` which have an explicit
+section about this topic.

sites/www/index.rst

@@ -13,6 +13,7 @@ usage and API documentation can be found at our code documentation site,
 
 .. toctree::
     changelog
+    faq
     installing
     contributing
     contact

sites/www/installing.rst

@@ -2,6 +2,8 @@
 Installing
 ==========
 
+.. _paramiko-itself:
+
 Paramiko itself
 ===============
 
@@ -23,6 +25,28 @@ PyCrypto C extension. `ecdsa` is easily installable from wherever you
 obtained Paramiko's package; PyCrypto may require more work. Read on for
 details.
 
+.. _release-lines:
+
+Release lines
+-------------
+
+Users desiring stability may wish to pin themselves to a specific release line
+once they first start using Paramiko; to assist in this, we guarantee bugfixes
+for at least the last 2-3 releases including the latest stable one. This currently means Paramiko **1.11** through **1.13**.
+
+If you're unsure which version to install, we have suggestions:
+
+* **Completely new users** should always default to the **latest stable
+  release** (as above, whatever is newest / whatever shows up with ``pip
+  install paramiko``.)
+* **Users upgrading from a much older version** (e.g. the 1.7.x line) should
+  probably get the **oldest actively supported line** (see the paragraph above
+  this list for what that currently is.)
+* **Everybody else** is hopefully already "on" a given version and can
+  carefully upgrade to whichever version they care to, when their release line
+  stops being supported.
+
+
 PyCrypto
 ========