Makefile: add ci tests
Merge branch 'expressions' of github.com:karlvr/consistent.js into expressions
Expressions: add $ as a valid expression property start char
Add scope.$.evaluate and scope.$.exec for running expressions programatically
Scope.$.get should not be able to access $ in the scope.

scope.$.get should be consistent with scope.$.snapshot, which obviously can't access $.

This also provides some expression security so expressions cannot access the functional parts of the scope.
Expression security: prevent any use of our getNestedProperty function from accessing object constructors or the Function constructor.

This is based on a suggestion by Mal Curtis and the security work by Angular in their expression parser:
https://github.com/angular/angular.js/blob/master/src/ng/parse.js
Test: expressions functionality and security
Test: expression statements