Work on #87

Implement a test suite, including Travis-CI integration

gpiozero/compat.py

@@ -0,0 +1,27 @@
+from __future__ import (
+    unicode_literals,
+    absolute_import,
+    print_function,
+    division,
+    )
+str = type('')
+
+import cmath
+
+
+# Back-ported from python 3.5; see
+# github.com/PythonCHB/close_pep/blob/master/is_close.py for original
+# implementation
+def isclose(a, b, rel_tol=1e-9, abs_tol=0.0):
+    if rel_tol < 0.0 or abs_tol < 0.0:
+        raise ValueError('error tolerances must be non-negative')
+    if a == b: # fast-path for exact equality
+        return True
+    if cmath.isinf(a) or cmath.isinf(b):
+        return False
+    diff = abs(b - a)
+    return (
+        (diff <= abs(rel_tol * b)) or
+        (diff <= abs(rel_tol * a)) or
+        (diff <= abs_tol)
+        )