title: Integrating Log-Normal PDF in sympy
body: <p>Why won't SymPy integrate a standard Log-Normal PDF to 1?</p>
  
  <p>I'm running the following code in Python 3.x and SymPy 1.0.1:</p>
  
  <pre><code>from sympy.stats import density, LogNormal
  from sympy import Symbol, integrate, oo
  
  mu, sigma = 0, 1
  z = Symbol('z')
  X = LogNormal('x', mu, sigma)
  f = density(X)(z)
  
  integrate(f, (z, 0, oo))
  </code></pre>
  
  <p>which should(?) return 1 but outputs:</p>
  
  <pre><code>sqrt(2)*Integral(exp(-log(z)**2/2)/z, (z, 0, oo))/(2*sqrt(pi))
  </code></pre>
  
  <p>Does anyone know what's going on here?</p>