Move rustapi_module into examples

This is really a test module, but the Rust convention is to put
something like this under examples/, and when it lands, we can take
advantage of "Project-based Examples for Cargo Projects" - RFC link
at https://github.com/rust-lang/rfcs/pull/2517

Cargo.toml

@@ -56,5 +56,4 @@ members = [
     "pyo3cls",
     "pyo3-derive-backend",
     "examples/*",
-    "tests/rustapi_module",
 ]

ci/travis/test.sh

@@ -7,11 +7,11 @@ cargo test --features $FEATURES
 
 for example in examples/*; do
   cd $example
-  python setup.py install
-  pytest -v tests
+  if [ -f tox.ini ]; then
+      tox -e py
+  else
+    pip install -e .
+    pytest -v tests
+  fi
   cd $TRAVIS_BUILD_DIR
 done
-
-cd tests/rustapi_module
-tox -e py
-cd $TRAVIS_BUILD_DIR