Fixed sequence string for oracle.
Tested that the next value feature worked for Oracle
Merge pull request #90 from vorbis/oracleFix

Fixed sequence string for oracle.
Documenting liquibase.change package and finalizing APIs
Merge remote-tracking branch 'origin/master'
renamed AbstractChangeTest to StandardChangeTest so I can create an actual AbstractChangeTest
Finished documentation, testing, and vetting of AbstractChange Object
Cleaned up exceptions on Change and AbstractChange