* Fighting continues near eastern city of Slaviansk
* Rebel leaders dismiss new president's inaugural speech
By Thomas Grove and Alissa de Carbonnel
SLAVIANSK/LUHANSK, Ukraine, June 7 (Reuters) - Pro-Russian separatists poured scorn on peace overtures from Ukraine's new president Petro Poroshenko on Saturday as fighting rumbled on in the east of the country.
Taking the oath of office in...