- Serialize breadcrumbs to prevent issues with binary data (getsentry…

…#538)

- Fix notice array_key_exists() expects parameter 2 to be array, null given (getsentry#527)

- Improve handling DSN with "null" like values (getsentry#522)

- Prevent warning in Raven_Stacktrace (getsentry#493)

- Add setters for the serializers on the `Raven_Client` (getsentry#515)

- Avoid to capture `E_ERROR` in PHP 7+, because it's also a `Throwable` that gets captured and duplicates the error (getsentry#514)

Release 1.7.1

Gracefully handle empty arguments context