Replace const.txt file input with synthetic inputs

This commit replaces file resource-based test inputs with in-memory
equivalents.  This is more consistent and efficient than the previous
approach.  Also resized some test inputs to be partSize + 1 instead of
2 * partSize.  Tested against aws-s3, blobstore, core, cloudfiles-us,
and filesystem.
[minor] `byte[] b`? Not sure which style we use elsewhere, but this seems to make it clearer that we're talking about a variable b of type "array of byte"? Compare also the InputStream [Javadoc](http://docs.oracle.com/javase/7/docs/api/java/io/InputStream.html)?