8.
若数列\(\{a_{n}\}\)满足\(a_{1}=-1,a_{n}=2a_{n-1}-1(n∈N^{*},n\geqslant 2)\).
\((1)\)求证:数列\(\{a_{n}-1\}\)是等比数列,并求数列\(\{a_{n}\}\)的通项公式;
\((2)\)设\(b_{n}=\log _{2}(1-a_{n})\),若数列\(\{ \dfrac {1}{b_{n+1}b_{n}}\}(n∈N^{*})\)的前\(n\)项和为\(T_{n}\),求证:\(T_{n} < 1\).