pre-commit and requirements

• added a pre-commit git-hook configuration
• lowered requirement for numpy. 1.12 is the 2017 version, which I choose arbitrarily, could potentially be higher, just the latest version is not supported yet e.g. by numba.

could close #1 (closed)

src/icartt/dataset.py

@@ -9,7 +9,7 @@ from enum import IntEnum
 import numpy as np
 
 
-DEFAULT_NUM_FORMAT = "%f"
+DEFAULT_NUM_FORMAT = "%g"
 DEFAULT_FIELD_DELIM = ", "