Add crop option.
Merge branch 'master' of https://github.com/carlossosa/Thumbnails.git
- Rewrite __construct method
- Replace save() method by saveAs()
- Rename printThumbnail by printImage and add $options parameter 
- Rename  getThumbnailAsString by getAsString and add $options parameter
- Improve autodetect of image type, now isn't is need specify image type in any method.
- Remove magic methods printThumbnailAs... and saveAs...
- Permit access to thumb and image resources using function getImageResource and getThumbnailResource
- Minor changes in doThumbnail method
- Limited support to png, gif, jpeg images.

TODO: Document and test new features. 
TODO: Add support for Bmp images.
TODO: Permit add watermark to thumbnail.
- Rewrite __construct method
- Replace save() method by saveAs()
- Rename printThumbnail by printImage and add $options parameter 
- Rename  getThumbnailAsString by getAsString and add $options parameter
- Improve autodetect of image type, now isn't is need specify image type in any method.
- Remove magic methods printThumbnailAs... and saveAs...
- Permit access to thumb and image resources using function getImageResource and getThumbnailResource
- Minor changes in doThumbnail method
- Limited support to png, gif, jpeg images.

TODO: Document and test new features. 
TODO: Add support for Bmp images.
TODO: Permit add watermark to thumbnail.
FIX: Transparent colors.