Merge pull request #16 from phenoscape/master

Added Ant tasks for downloading WordNet.
Added code to handle empty return or failure to methods getSingular() and getPlural() in WordFormUtility class.
Added logger to methods addSingularPluralPair() and updateTable(). Fixed a bug in method updateTable().
Merge branch 'master' of https://github.com/dongyemeng/charaparser-unsupervised
1) Added a utility method, addSentence(), to DataHolder class. 2) Added log4j logger to methods populateUnknownWords(), addStopWords(), addCharacters(), addNumbers(), addClusterstrings(), addProperNouns()
Fixed a bug in getPOSptn()
1) Added some log msg into method addStopWords(). 2) Fixed a bug in method getPOSptn().
Fixed a bug in method getFirstNWords(), by adding a new utility method, getSentenceHead(). Have not tested yet.
Added all test cases to method getSentenceHead(). Fixed two bugs in the method.
1) Added method getSentenceHead() to method getFirstNWords(). 2) Fixed a bug in method getPOSptn().
Added several test cases of method getSentenceHead(). Fixed several bugs of it.
updated readme
1) Renamed method addClusterstrings() to addClusterStrings(). 2) Added new content to readme file.
Added Apache Commons Lang library into the project.
Replaced equalsWithNull() method in StringUtility class by equals() method in StringUtils class from Apache Commons Lang library.
1) Added new content to readme file. 2) Added log4j logger to method updateUnknowWord(). 3) Added two new utility methods into DataHolder class, which are getWordPOSEntries(), updateWordPOS(). 4) Fixed a bug in method markKnown(). 5) Fixed a bug in method updatePOS(). 6) Override toString() method in WordPOSKey class and WordPOSValue class.
Added some log msg into methods updatePOS() and doItHelper(). Fixed a bug in case 3 of method doItHelper(). Redesigned the test cases for case 1 and case 3.2 of method doItHelper().
1) Added key word Override to all methods override a method in parent class in all class. 2) Replaced the implementation of hashCode() method in all classes by an implementation using the HashCodeBuilder from Apache Commons Lang library.
1) Added key word Override to all methods override a method in parent class in all class. 2) Replaced the implementation of hashCode() method in all classes by an implementation using the HashCodeBuilder from Apache Commons Lang library.
Added some comments, and updated the readme file.