Duplicate pager options before paginating

Without this fix, the options.update will affect existing instantiations
of pager. So, if you call account.invoices.past_due, account.invoices
will from then on have the past_due scope applied.

Signed-off-by: Stephen Celis <stephen@stephencelis.com>
Properly escape params

Subscription#postpone, for example, accepts Time, which, #to_s, returns
a string with spaces in it. This fix ensures that parameters are escaped
before being appended to the URI.

Signed-off-by: Stephen Celis <stephen@stephencelis.com>
2.1.8: Bug fixes

- Don't apply scope options to original associations
- Accept Time objects for Subscription#postpone

Signed-off-by: Stephen Celis <stephen@stephencelis.com>