Added exception handling to paperclip:refresh:thumbnails rake task.

https://github.com/thoughtbot/paperclip/issues/760
Switched log_error output stream to STDERR.
Merge branch 'rake-task-exception-handling' of git://github.com/holetse/paperclip into holetse-rake-task-exception-handling
Add content_type and size errors to base attribute

This propagates attachment size and content_type validations to the main
attachment attribute, to make them behave the same as presence
validations. This allows paperclip to play more nicely with simple_form
and other form abstraction gems.

This commit includes a behaviorial change. If you emit all errors on a
model instance you will see some failed validations twice: once for the
base attachment attribute and again for the failed presence,
content_type or size attachment attributes.
Call out problems with parallel tests in the README

Thanks to ericsullivan for pointing this out.
Refactor adding content_type errors to base attribute
Should be agnostic toward ActiveRecord; use ActiveModel where appropriate
fix typo in README.md
Merge pull request #1280 from willchapin/master

Fixes a typo in the README.md
Revert Paperclip::Storage::Filesystem#flush_writes

This commit makes this method move by default instead of copying, which
should make it perform significantly better with large files. It falls
back to the old semantics if the mv fails.
Refactor Paperclip::Attachment to eliminate code duplication between #extra_options_for and #extra_source_file_options_for
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Validate the attachment before we attach without calling valid?

Using the ActiveRecord validations is smart in order to lessen load on
the project to develop our own validators, but it's problematic in that
calling `valid?` on the record fires off all the other validations --
including those on fields which may not be set yet because of
mass-assignment. This commit will "pre-validate" the attachment's fields
so that it doesn't process an invalid attachment, but it does so by
running its validations manually on assignment.
Merge pull request #1281 from johnnyshields/master

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Make #expiring_url behavior consistent with #url

Return the default path when the attachment has no remote file
Assigning an empty string does nothing
Ensure correct behavior when assigning empty string
fix for mocha's warning
ability to define custom sanitizers for filenames
Adds a FilenameCleaner class

You can either specifiy :restricted_characters or you can define your
own :filename_cleaner object. This object needs to respond to #call and
takes the filename that will be cleaned. It should return the cleaned
filenme.