Big changes and packaged the classes.

1. Repaired bugs about file path names: When the working directory on
hadoop is "/" function getWorkingDirectory returns "/". When the working
dir is others, say, "/user/home/", the function returns "/user/home". So
a judgement about the hash needs to be done.
2. Packaged the demo program into the package as the function to call.
Therefore, use com.sari.luceneonhadoop.IndexFiles to index a folder,
com.sari.luceneonhadoop.SearchFiles to search a keyword,
com.sari.luceneonhadoop.CatFile to display a file with an absolute file
path name returned by SearchFiles.