doc(index): link to doc.rs for APIs

We also link more specifically to crates.io.

Some debt was taken on as the build_version is special and
duplicated right now.

src/mako/cli/lib/argparse.mako

@@ -84,7 +84,7 @@ Configuration:
 <%def name="new(c)" buffered="True">\
 <%
     doc_base_url = cargo.doc_base_url + '/' + os.path.dirname(api_index(cargo.doc_base_url, name,
-                                                                        version, make, check_exists=False))
+                                                                        version, make, cargo, revision, check_exists=False))
     url_info = "All documentation details can be found at " + doc_base_url
 
     # list of tuples