Move the implementations of encoding_overhead() etc back to the Python file

I commented to contributor robamu that it would be good to put the functions
in _cobs_py.py etc, instead of __init__.py, and then add an equivalent C API
implementation in the .c files. However --

* robamu doesn't have experience with the Python C API.
* I haven't used the Python C API for years.
* These functions aren't as calculation-intensive as the encode/decode
  functions are, and aren't expected to be a hotspot in typical usage.

So for now, I'll just move these functions back into __init__.py.

This pertains to pull request #3.

Author: cmcqueen

python3/cobs/cobs/__init__.py

@@ -26,3 +26,17 @@
 DecodeError.__module__ = 'cobs.cobs'
 
 from .._version import *
+
+
+def encoding_overhead(source_len):
+    """Calculates the maximum overhead when encoding a message with the given length.
+    The overhead is a maximum of [n/254] bytes (one in 254 bytes) rounded up."""
+    if source_len == 0:
+        return 1
+    return (source_len + 253) // 254
+
+
+def max_encoded_length(source_len):
+    """Calculates how maximum possible size of an encoded message given the length of the
+    source message."""
+    return source_len + encoding_overhead(source_len)

python3/cobs/cobs/_cobs_py.py

@@ -88,17 +88,3 @@ def decode(in_bytes):
             else:
                 break
     return bytes(out_bytes)
-
-
-def encoding_overhead(source_len):
-    """Calculates the maximum overhead when encoding a message with the given length.
-    The overhead is a maximum of [n/254] bytes (one in 254 bytes) rounded up."""
-    if source_len == 0:
-        return 1
-    return (source_len + 253) // 254
-
-
-def max_encoded_length(source_len):
-    """Calculates how maximum possible size of an encoded message given the length of the
-    source message."""
-    return source_len + encoding_overhead(source_len)

python3/cobs/cobsr/__init__.py

@@ -20,3 +20,16 @@
 
 from .._version import *
 
+
+def encoding_overhead(source_len):
+    """Calculates the maximum overhead when encoding a message with the given length.
+    The overhead is a maximum of [n/254] bytes (one in 254 bytes) rounded up."""
+    if source_len == 0:
+        return 1
+    return (source_len + 253) // 254
+
+
+def max_encoded_length(source_len):
+    """Calculates how maximum possible size of an encoded message given the length of the
+    source message."""
+    return source_len + encoding_overhead(source_len)

python3/cobs/cobsr/_cobsr_py.py

@@ -96,17 +96,3 @@ def decode(in_bytes):
             else:
                 break
     return bytes(out_bytes)
-
-
-def encoding_overhead(source_len):
-    """Calculates the maximum overhead when encoding a message with the given length.
-    The overhead is a maximum of [n/254] bytes (one in 254 bytes) rounded up."""
-    if source_len == 0:
-        return 1
-    return (source_len + 253) // 254
-
-
-def max_encoded_length(source_len):
-    """Calculates how maximum possible size of an encoded message given the length of the
-    source message."""
-    return source_len + encoding_overhead(source_len)