Changes from 4.0.1 to 4.1a:

    Bump version number prior to 4.1a release
    Escape only RFC 3986 specified "reserved" characters
    Be much more aggressive about keyword URL encoding
    Guard against non-nil but empty song info strings
    Watch out for empty keyword strings
    Use Objective-C 2.0 fast enumeration for keyword preprocessing
    Additional logging (search keywords)
    Use Amazon-related macros instead of hard-coded strings
    Rewrite cover downloader using newer Mac OS X XML APIs
    Use WOAmazonLog to audit Amazon ECS 4.0 compliance
    Add custom logging function for Amazon events
    Bump version number post-release