Adds tests for behavior init function.
Makes Behavior init function test pass, Also:

- Covers the case that init function is undefined.
Multiple behaviors(issue #3) : adds tests cases to cover the scenario of the same behavior attached to multiple elements
Multiple behaviors(issue #3): adds the missing pieces of logic making the crawl function behave as spected
Merge pull request #5 from roperzh/issue-3

[Fix #1] - Allow multiple elements with the same behavior
Merge pull request #4 from bernardocorbella/issue-2

[ Fix #2 ] - Behavior initialization
Test suite improvments: adds a missing scenario for the Behavior#init function
Test suite improvments: changes a message in the Essential.Core#crawl function
Merge pull request #7 from roperzh/issue-6

[ Fix #6 ] Test suite improvments
Adds a new build files for the 0.2.0 release
Release: set the 0.2.0 version tag in the bower.json and package.json files
Adds missing annotated documentation for the Behavior#init function
Fixes a grammar typo in the description of Essential.Behavior