Enable no-redeclare

Disallow Redeclaring Variables (no-redeclare)

In JavaScript, it's possible to redeclare the same variable name
using var. This can lead to confusion as to where the variable is
actually declared and initialized.

http://eslint.org/docs/rules/no-redeclare

Change-Id: I0ef2febe67700532d748327f9a0f10f846c7ae80

.eslintrc

@@ -336,7 +336,7 @@ rules:
 
   # Disallow declaring the same variable more than once
   # http://eslint.org/docs/rules/no-redeclare
-  no-redeclare: 0 # TODO(krotscheck): Discuss & Activate
+  no-redeclare: 2
 
   # Disallow use of assignment in return statement
   # http://eslint.org/docs/rules/no-return-assign