* Use StringBuilder instead of StringBuffer class
* Denote utility class
* Reformat code.
Put HtmlTextConverter.java into test harness

All the file readers are done in Java 7 manner, that is, using try-with-resources
statements. More readable this way.

Some files need to be used in the test and they are added in testresources directoy.
One more test for HtmlTextConverter.java with more advance file content