Fix bug when SALESFORCE_DB_ALIAS not defined in settings.py

SALESFORCE_DB_ALIAS is listed as an optional settings variable.

Mimic the use of sf_alias in router.py.
Merge pull request #25 from jacobwegner/fix-reauthentication-bug

Fix bug when SALESFORCE_DB_ALIAS not defined in settings.py
Override WhereNode from django.db.models.sql.where to use SOQL NOT.

SQL negation: SELECT foo FROM bar WHERE Status = ‘Awesome’ NOT( Having_fun = false AND Out_of_cash = false)
SOQL negation: SELECT foo FROM bar WHERE Status = ‘Awesome’ AND (NOT( Having_fun = false) AND NOT(Out_of_cash = false))
Test that exclude query construction returns a queryset
Fix typ in docstring.
CursorWrapper eroneously sending connection_created signal a second time (and sends itself, instead of a Connection Object).  This can cause handlers listening to that signal to fail
Add conditional for Django 1.5 or 1.6 to override their version of WhereNode.as_sql
prior to django1.6 it was on you to send this signal, typically just after the Cusor gets set up
fixed tabbing, updated editorconfig
comment, typo
centralized DJANGO_* compat variables
Merge pull request #27 from sbussetti/double-connection-signal

CursorWrapper eroneously sending connection_created signal a second time...
Merge branch 'pr/26'

Conflicts:
	salesforce/backend/compiler.py
Update AUTHORS.md