Update node tests to match versions actually installed

tests/base/node10/README.md

@@ -1 +1 @@
-Test that node 10 is installed and runnable.
+Test that node 10 and npm 6 are installed and runnable.

tests/base/node10/verify

@@ -2,6 +2,9 @@
 
 set -e
 which node
+node --version
 node --version | grep v10
+
 which npm
-npm --version | grep 6.2
+npm --version
+npm --version | grep 6.4