设数列\(\{a _{n} \}\)满足\(a _{1} =2\)，\(a _{n+1} =a _{n} +2 ^{n}\)．
\((1)\)求数列\(\{a _{n} \}\)的通项公式；
\((2)\)设\(b _{n} =\log _{2} (a _{1} \boldsymbol{⋅}a _{2} …a _{n} )\)，求数列\(\{ \dfrac {1}{b_{n}} \}\)的前\(n\)项和\(S _{n}\)．