Add .DS_Store and *.jpg to .gitignore
Use the specified directory in image search path

This actually fixes a bug that prevented the specified directory from
being used.
Add more detailed comments to upload.rb
Add the exists_in? method to the Image class

Call exists_in? to determine whether an image already exists in a
bucket.
Use File.expand_path and JPG in image search path

Use File.expand_path to expand "~" to the home directory and add the
upper-case "JPG" extension to the list of files to search for.
Insert a delay into the progress bar thread

Make the progress bar thread sleep for one second before it tries to pop
a value off of an empty queue. Hopefully this will fix the deadlock
crashes that I was experiencing earlier.

(Interestingly enough, those crashes don't appear to have prevented any
images from being uploaded; they simply caused the command-line program
to abort.)

NOTE: This program really needs to stop launching a new thread
immediately every time it finds a new image. Only 5-10 threads should be
active at a time (ideally the same number of threads as there are
available processor cores).
Update puts and printf statements in upload.rb

Pad the filenames to a width of 50 characters and show file sizes.
Check for uploaded files in upload.rb
Remove unnecessary comments from upload.rb
Update README and TODO

This program can now recursively upload files and show a progress bar.
Add a FAQ entry on this project's Ruby version