README, .gitignore

Update building instructions and add tests/atconfig to .gitignore.
diff --git a/.gitignore b/.gitignore
index 8bc903b..9a8f70b 100644
--- a/.gitignore
+++ b/.gitignore
@@ -15,3 +15,11 @@
 Makefile.in
 Makefile
 Makefile.am.sample
+src/tests/atconfig
+src/tests/hnb-test
+src/tests/package.m4
+src/tests/test-helpers
+src/tests/test-hnbap
+src/tests/test-ranap
+src/tests/testsuite
+src/tests/testsuite.log