Reset crops

Added possibility to remove generated crops, e.g. if original has changed
Merge pull request #53 from bigbozo/dev-updateimage

Added possibility to remove generated crops, e.g. if original has changed.
Renaming variables from pull request to match my conventions
Renaming variables from pull request to match my conventions
Merge branch 'master' of git://github.com/BKWLD/croppa

# By Robert Reinhard
# Via Robert Reinhard
* 'master' of git://github.com/BKWLD/croppa:
  Renaming variables from pull request to match my conventions