docs: Adding example of how to build ndnSIM using non-root-installed boost libraries

This commit also includes an example of how to build boost libraries
with one of the known pitfalls.

closes #8
diff --git a/docs/source/index.rst b/docs/source/index.rst
index db110f4..3a2f47e 100644
--- a/docs/source/index.rst
+++ b/docs/source/index.rst
@@ -12,3 +12,4 @@
    helpers
    applications
    examples
+   boost-custom-install