Add travis-ci integration, strip_space & sanitize_string method

Hello,

I've made minors changes :

* added a `phpunit.xml.dist` file in the root folder (allow integration into several IDE and continuous integration servers)
* added a `.travis.yml` file at root (allow integration with travis-ci.org see below the build button)
* added a `utils::strip_space` method. It remove all white-spaces from the given string.
* added a `utils::sanitize_string` method. It remove whitespaces + punctuation characters + accents and lower the string.
* correct the `DateTime` call (added the root namespace)

The doc is updated, code unit-tested : [![Build Status](https://travis-ci.org/lilobase/utilphp.png?branch=master)](https://travis-ci.org/lilobase/utilphp)