Sweep for pep8 problems and common python gotchas.

Some python gotchas:
- id is a builtin method-- it's generally preferred not to overwrite it in any scope
- Comparisons with against booleans and None should use `is` instead of ==
- Default arguments should not be mutable, since they are defined at the methods define time.
- Naked exception catching is generally considered bad practice. I didn't fix all of these because I didn't want to risk breakages without unit tests.

Otherwise I made a sweep for formatting to match pep8 conventions. Read more about python formatting conventions here: https://www.python.org/dev/peps/pep-0008
I am partial to

```
json.dumps(args, to, 80, chars,
           extra_args, go_here)
```

Rather than having each argument on a separate line.

For this example though it might work better to do something like

```
return '<%s%s at %s> JSON: %s' % (type(self).__name__, type_string, hex(id(self)),
                                  json.dumps(self.to_dict(), sort_keys=True, indent=2,
                                             cls=EasyPostObjectEncoder))
```

And since the `json.dumps` call is long it might be useful to make it a variable.