Change some error tests to use `assert_raises` (#847)
Change some error tests to use `assert_raises` (#847)

Previously, we had quite a few error tests that were written like this:

``` ruby
begin
  client.execute_request(:post, "/v1/charges")
rescue Stripe::InvalidRequestError => e
  assert_equal(404, e.http_status)
  assert_equal(true, e.json_body.is_a?(Hash))
end
```

The trouble with that pattern is that although they'll _usually_ work,
the test will incorrectly pass if no error at all is thrown because the
`rescue` never activates and therefore the assertions never run.

We change them to use `assert_raises` like so:

``` ruby
e = assert_raises Stripe::InvalidRequestError do
  client.execute_request(:post, "/v1/charges")
end
assert_equal(404, e.http_status)
assert_equal(true, e.json_body.is_a?(Hash))
```

The weird part is that many of the tests were already using
`assert_raises`, so here we're just converting them all over to use the
same convention.

I've also made a few whitespace tweaks. None of them are significant,
but they were an attempt to standardize a little on the whitespace
layout of many of these tests which were similar.
stripe/stripe-ruby