Zend_Service_Twitter_TwitterTest float failure

Fixes failure when the big int is converted to float.

```
1) Zend_Service_Twitter_TwitterTest::testShowStatusReturnsResponse
Failed asserting that two strings are equal.
--- Expected
+++ Actual
@@ @@
-https://api.twitter.com/1.1/statuses/show/307529814640840705.json
+https://api.twitter.com/1.1/statuses/show/3.0752981464084E+17.json
```