Simplifying some code structure.

- basically removing an always encountered `else` path
- applying proper Array function as it's supposed to be available in all browsers using Canvas
Added segment testsuite
Testing segments API

- adding sinon for stubs
- minor tweaks, like `==` -> `===` or parenting an anonymous function
Adding test coverage for the actual use case.

Also removed an uneeded call for drawing, having a *2 impact.
Last minute rendering.
Merge pull request #5 from bbcrd/feature-5-segments-performance

[READY] Segments performance boost