Reverts a default behaviour that was changed in a previous commit.

[This commit](https://github.com/dan-coulter/phpflickr/commit/fe6f493de1aabe0a34d50fa7bab489494716942f#diff-9b9a87a6f1636876e0a3987693811e9cR319) changed the default behaviour of the `request()` function to *not* clean text nodes as they come in, resulting in drastic structural changes to almost all data coming back from Flickr.

This update reverts the code back to the original behaviour (but still with mikeMTOL's improvements) so it will not break any apps that have already been using phpFlickr and decide to update.

I guess the problem here is that (I think) this fix solves between three to five current issues logged with the repository (https://github.com/dan-coulter/phpflickr/issues/48, https://github.com/dan-coulter/phpflickr/issues/36, https://github.com/dan-coulter/phpflickr/issues/41, https://github.com/dan-coulter/phpflickr/issues/25, and https://github.com/dan-coulter/phpflickr/issues/23) but I understand that whilst this saves existing apps that have *updated* their phpFlickr submodule, it will potentially break new apps that have been using phpFlickr since [this commit](https://github.com/dan-coulter/phpflickr/commit/fe6f493de1aabe0a34d50fa7bab489494716942f#diff-9b9a87a6f1636876e0a3987693811e9cR319) on the 26th of May.

I'll submit this pull request and leave comments on all issues I think are affected. I'll leave the choice to merge up to @dan-coulter.