Refactor code and add docs

Refactored the code inside the brian2units and also made
the setup for sphinx and readthedocs.

Signed-off-by: Sorin Birchi <sb.birchi.sorin@gmail.com>

.readthedocs.yaml

@@ -0,0 +1,21 @@
+# .readthedocs.yaml
+# Read the Docs configuration file
+# See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
+
+# Required
+version: 2
+
+# Set the OS, Python version and other tools you might need
+build:
+  os: ubuntu-latest
+  tools:
+    python: "3.x"
+
+# Build documentation in the "docs/" directory with Sphinx
+sphinx:
+  configuration: docs_sphinx/conf.py
+
+post_install:
+    - python -m pip install .
+    - python -m pip install -r rtd-requirements.txt
+

__init__.py

@@ -1,5 +1,3 @@
 """
 brian2units
 """
-
-from brian2units.units.unitsafefunctions import arange, linspace