add option for resampling filter
change wording of unsupported filter exception
Merge branch 'feature/opt-resampling-filter' of https://github.com/havvg/Imagine into havvg-feature/opt-resampling-filter

Conflicts:
	lib/Imagine/Imagick/Image.php
Add unit tests on image resolution option
Merge pull request #319 from romainneutron/havvg-feature/opt-resampling-filter

Add option for resampling filter