NEW Implemented a function for converting std. dev. to 95% conf. intervals.

Implemented convert_std_95ci() function and added it to the stats module.
Also added a small testing example of this function.
PEP8 Added double line spaces for top-level classes, functions, ...
NEW Added the ability to plot different error measures (e.g. 95% conf. intervals).

Augmented the combine_experiment_results() function to handle different error measures (currenlty, std. deviation and 95% conf. intervals).
Modified the testing configurations to use this new feature.
ENH Added the ability of running experiments for multiple MTL problems from the same synthethic_test run.

Changed the testing configurations 41 -- 44 to handle multiple values of the data_rnd_seed parameter, which is responsible for generating different MTL problems.
RESULT Added results of experiments on synthetic Boolean data with changing # of tasks/group.
RESULT Added results of experiments on synthetic Boolean data with changing # of tasks groups.
RESULT Added results of experiments on synthetic Boolean data with changing # of examples/task.
RESULT Added results of experiments on synthetic Boolean data with changing value of the noise parameter.
FIX Added proper handling of a corner case when generating Boolean functions.

In function generate_boolean_function(), empty disjuncts are now discarded since expression 'And(*disjunct)' would return value True for them and consequentially, the whole Boolean function would simplify to the value True.
RESULT Added additional results of experiments on synthetic Boolean data with changing # of tasks/group (for 20 tasks/group).
RESULT Added additional results of experiments on synthetic Boolean data with changing # of task groups (for 20 task groups).
RESULT Added additional results of experiments on synthetic Boolean data with changing # of task groups (for 20 task groups and data_rnd_seed == 17).
ENH Implemented a simple function for pretty-printing iterables.

The pprint_iter() function returns the items of the given iterable separated by commas. It is used for naming some outputted PDF files so that LaTeX won't have issues with them.
RESULT Added PDFs showing plots of combined results of experiments on synthetic Boolean data.
FIX Added proper handling of a corner case when using _draw_subplot().

If the _draw_subplot() function was given x_tick_points list with only one item, then the _draw_subplot() function would raise an exception since its automatic adjustment of x-axis' left and right limits need at least 2 points.
NEW Completely reworked the testing configurations' code in synthetic_test module.

Moved the code into private functions and added ability to change some of the testing configurations' parameters when calling the private functions.
Added a new testing configuration for the experiments with a changing base learner.