Definite Integral of a Piecewise Function

Let $f$ be the function defined by $f(x) = \begin{cases} x^2 & \text{for } x < 0 \\ -1 & \text{for } x = 0 \\ x & \text{for } x > 0 \end{cases}$. What is the value of $\displaystyle \int_{-1}^{1} f(x) \, dx$?