Update tox.ini to use {posargs} to configure nosetests.

To override defaults, use
  `tox -- --your --nosetest --options --here`
Update default nosetest settings to use verbose logging and show test ids
add .coverage and .noseids to .gitignore
Add example for running single unit test to README

.gitignore

@@ -6,3 +6,5 @@ dist
 MANIFEST
 env
 servers/*/kafka-bin
+.coverage
+.noseids

README.md

@@ -190,6 +190,11 @@ pip install python-snappy
 tox
 ```
 
+## Run a single unit test
+```shell
+tox -e py27 -- -v --with-id 102
+```
+
 ## Run the integration tests
 
 The integration tests will actually start up real local Zookeeper

tox.ini

@@ -8,6 +8,6 @@ deps =
     mock
     python-snappy
 commands =
-    nosetests --with-coverage --cover-erase --cover-package kafka []
+    nosetests {posargs:-v --with-id --with-coverage --cover-erase --cover-package kafka}
 setenv =
     PROJECT_ROOT = {toxinidir}