Fix "Complexity" issue in kyu_4/human_readable_duration_format/format_duration.py

[ikostan]

Cyclomatic complexity is too high in function format_minutes. (6)

https://codeclimate.com/github/iKostanOrg/codewars/kyu_4/human_readable_duration_format/format_duration.py#issue_672c403bc11fdc000100090f

[ikostan]

Cyclomatic Complexity

Cyclomatic Complexity corresponds to the number of decisions a block of code contains plus 1. This number (also called McCabe number) is equal to the number of linearly independent paths through the code. This number can be used as a guide when testing conditional logic in blocks.

Radon analyzes the AST tree of a Python program to compute Cyclomatic Complexity. Statements have the following effects on Cyclomatic Complexity:

Construct | Effect on CC | Reasoning -- | -- | -- if | +1 | An if statement is a single decision. elif | +1 | The elif statement adds another decision. else | +0 | The else statement does not cause a new decision. The decision is at the if. for | +1 | There is a decision at the start of the loop. while | +1 | There is a decision at the while statement. except | +1 | Each except branch adds a new conditional path of execution. finally | +0 | The finally block is unconditionally executed. with | +1 | The with statement roughly corresponds to a try/except block (see PEP 343 for details). assert | +1 | The assert statement internally roughly equals a conditional statement. Comprehension | +1 | A list/set/dict comprehension of generator expression is equivalent to a for loop. Boolean Operator | +1 | Every boolean operator (and, or) adds a decision point.

Source: http://radon.readthedocs.org/en/latest/intro.html