hdlib v0.1.15

hdlib v0.1.15

Add:

• Add examples/chopin2_iris.sh as a test case for examples/chopin2.py;
• Add new unit tests to test/test.py.

Fix:

• space.Space.bulk_insert has been refactored to make use of space.Space.insert;
• parser.load_dataset now throws a ValueError in case of non-numerical datasets;
• Add missing import os in space.Model.