#30: changed HDFSUtils.readLines(...) to return a list of Strings - one for each line: better representation of a file which could contain duplicate lines, deduplication is not always required

Made getFilesCount independent of data source (takes in List<String>): better testable.

Removed HDFSUtils.writeProfessionCounts(...): following Pito's golden rule "don't optimize until you have to". getProfessionCounts(...) works in under 3 seconds with the original profession_test.txt. No need to write the counts into a file and read it in later.
#30: refactored the tests. Added getProfessionCounts(...) performance test.
The performance test shows that reading in the whole profession_train.txt with over 673k article -> professions assignments as well as parsing and counting - all in total - takes less than 5 seconds. Thus we don't need methods to write and read the counts into / from a separate file.
#30: added JUnit test for HDFSUtils.getProfessionCounts(...).
Closes #30.
Merge branch 'master' into Calvin.21.JUnitProfessionIndex
included haram's ProfessionIndexMapred
Merge branch 'master' into Calvin.21.JUnitProfessionIndex
updated ProfessionIndexMapred with some minor bugfixes (e.g. Set<String> peopleLines to List<String>, parameters in mapper, etc.) Commented out the reducer class related stuff, as it's not fully implemented yet. Implemented mapper test function in ProfessionIndexMapredTest. Imported necessary dependencies (in MRUnit folder). CURRENT PROBLEM: ProfessionIndexMapper causes an out of memory error in Java heap space. Would this problem occur on cluster?