Feature/alias (#800)

Implement model aliasing

Co-authored-by: Brian Abelson <abelsonlive@users.noreply.github.com>
Co-authored-by: Jonathan Kaczynski <jon-rtr@users.noreply.github.com>

automatic commit by git-black, original commits:
  540631f

core/dbt/exceptions.py

@@ -872,7 +872,7 @@ def raise_ambiguous_alias(node_1, node_2, duped_name=None):
 
     raise_compiler_error(
         'dbt found two resources with the database representation "{}".\ndbt '
-        'cannot create two resources with identical database representations. '
+        "cannot create two resources with identical database representations. "
         'To fix this,\nchange the configuration of one of these resources:'
         '\n- {} ({})\n- {} ({})'.format(
             duped_name,