Only print coverage report to console on success.

This makes it much easier to see errors when they happen.

Also:
- Make ./scion.sh test and ./scion.sh coverage work with test filenames
  directly. E.g., this now works:
    ./scion.sh coverage test/lib_zookeeper_test.py
- Cleaned up .gitignore a bit, making patterns anchored at the root of
  the repository when applicable (as this was hiding some issues).

.coveragerc

@@ -3,3 +3,8 @@ exclude_lines =
   pragma: no cover
   def __repr__
   def __str__
+  raise NotImplementedError
+[run]
+omit = external/*
+[html]
+title = SCION unit test coverage

.gitignore

@@ -26,11 +26,10 @@ Thumbs.db
 
 # SCION generated files #
 #########################
-logs/*
-topology/ISD*
-topology/SIM
-topology/conf-gen
-traces/*
+/logs/
+/topology/ISD*/
+/topology/SIM/
+/traces/
 
 
 # Python generated files #
@@ -45,19 +44,19 @@ __pycache__
 
 # Crypto library generated files #
 #########################
-lib/crypto/python-tweetnacl-20140309/build/
+/lib/crypto/python-tweetnacl-20140309/build/
 
 
 # Documentation and Environment files
 #########################
-sphinx-doc/_build/
-venv/
+/sphinx-doc/_build/
+/venv/
 
 # Docker working directory
 ##########################
-docker/_build/
+/docker/_build/
 
 # Test coverage
 ##########################
-.coverage
-htmlcov/
+/.coverage
+/htmlcov/

scion.sh

@@ -42,13 +42,13 @@ cmd_status() {
 }
 
 cmd_test(){
-    PYTHONPATH=. nosetests -w test "$@"
+    PYTHONPATH=. nosetests "$@"
 }
 
 cmd_coverage(){
     set -e
-    PYTHONPATH=. nosetests --with-cov -w test "$@"
-    coverage html --omit 'external/*'
+    PYTHONPATH=. nosetests --with-cov --cov-report html "$@"
+    coverage report
     echo "Coverage report here: file://$PWD/htmlcov/index.html"
 }