Fixed issue #230 -- Avoid queries in aborted transactions

On PostgreSQL when the transaction is in aborted status, checking
connection.isolation_level will result in an error.
Made usable connections with alias not in db.connections
Made possible to use DJANGO_SETTINGS_MODULE in testing

Also added a dummy test_pgsql settings file.
Tests for issue_230
Fixed issue #230 -- prevent crash when transaction is in error state

fix for ticket https://github.com/django-debug-toolbar/django-debug-toolbar/issues/230
if isolation_level is looked up while transaction is in an error state, an exception is thrown, which eats up the original exception that is never shown
Add EXPLAIN ANALYZE for Postgres
Fix displaying instance of RawQuerySet in templates toolbar
Merge pull request #322 from mattrobenolt/fix-static-urls

Fix static assets
Fixed CSS according to standarts
Fix doc for show_toolbar.
fix hashcompat deprecation warnings with django 1.5
Merge pull request #291 from valsteen/master

prevent crash due to SQLDebugPanel when transaction is in error state
Merge pull request #336 from craigds/master

fix hashcompat deprecation warnings with django 1.5
Merge pull request #335 from fossilet/master

Fix doc for show_toolbar
Python 2.5 compatibility #261
Avoid importing `django.conf.urls.defaults` on django 1.4+
Use the built-in json module on python >= 2.6.

`django.utils.simplejson` is pending deprecation as
of django 1.5 and will be removed in 1.7.
Merge pull request #350 from charettes/simplejson

Use the built-in json module on python >= 2.6.
Merge pull request #349 from charettes/django-1.5-compat

Avoid importing `django.conf.urls.defaults` on django 1.4+
Updated example to use class-based generic views

Django dropped the function-based generic views in favor of class-based generic views. 
The transition is outlined here: https://docs.djangoproject.com/en/1.4/topics/generic-views-migration/