Added support for truncation of Strings, Arrays and Objects

> This is a replacement Pull Request for [pull/18](https://github.com/cloudhead/eyes.js/pull/18)

Added support for limiting the output of Strings, Arrays and Objects. This is done with three optional parameters: `maxStringLength`, `maxArrayLength` and `maxObjectKeys`. This will truncate the output to length to keep the output limited (e.g. for logging).

By default no truncation takes place. Pay attention however: truncation may hide certain elements you may want to display.

Tests cases are included in test/eyes-test.js.