#23: changed the key-value separator from '\t' (tab, default) to ' : ' as requested in the assignment.
#23: first (untested) implementation of Mapred for 3.3.
#23: first (untested) implementation of Mapred for 3.3.
#23: refactored parameter types of helper methods
#23: merged in StringDouble etc.
#23: made sure lemmas with 100% probability for a certain profession are not ignored because of log(1.0) == 0.
#23: fixed a bug with storing the top 3 professions in TopProfessions
#23: added test input files and calculated the expected output for a ProfessionClassifierMapred MapReduce JUnit test.
#23: getting expected output on cluster
#23: changed key-value separator to the required " : "
Closes #23.