Fix minor typo in comment.
Add comments to other code paths.
Call toLowerCase on file name only. Fixes break on case-sensitive file systems.
Specify Implementation-Title and Implementation-Vendor in built JAR file.

Relates to issue #22.

For example:

    Manifest-Version: 1.0
    Ant-Version: Apache Ant 1.8.2
    Created-By: 1.6.0_33-b33 (Sun Microsystems Inc.)
    Main-Class: com.drew.imaging.ImageMetadataReader
    Implementation-Title: metadata-extractor
    Implementation-Vendor: Drew Noakes
    Implementation-Version: 2.7.0
Consistent comment style.
XML formatting.
Add JAR plugin to POM file that sets values in manifest. Relates to #22.