Fixes #98 - Moved API & MapReduce classes to their own module.
Organized packages in core module.  Created FluoFactory class so users
can create FluoClient or FluoAdmin from API using reflection.  Core now
generates test jar to allow other modules to use utility test classes.
Formatted Maven pom files to use two spaces.  Configuration class was
renamed to Environment.
Merge pull request #120 from mikewalch/fluo-98-pull

Fixes #98 - Moved API & MapReduce classes to their own module.
Fixes #122 - Removed Range dependency in Span.  This allowed the
SpanUtil and ByteUtil classes to be moved from API to core module.