doc: recompile when testing in CONTRIBUTING.md

Changes to core modules does not take effect before project gets
recompiled. Tip new contributors about this when describing how to
to run tests in contribution guide.

Removed `jslint` from first test command example as jslint are included
when running `make test`.

Fixed wrong path of example stream2-transform test.

PR-URL: #2051

CONTRIBUTING.md

@@ -126,7 +126,7 @@ test/parallel/ directory.  Look at other tests to see how they should be
 structured (license boilerplate, common includes, etc.).
 
 ```text
-$ make jslint test
+$ ./configure && make -j8 test
 ```
 
 Make sure the linter is happy and that all tests pass.  Please, do not submit
@@ -142,9 +142,11 @@ $ python tools/test.py -v --mode=release parallel/test-stream2-transform
 You can run tests directly with iojs:
 
 ```text
-$ iojs ./test/parallel/test-streams2-transform.js
+$ ./iojs ./test/parallel/test-stream2-transform.js
 ```
 
+Remember to recompile with `make -j8` in between test runs if you change
+core modules.
 
 ### Step 6: Push