title: element wise test of numpy array is numeric
body: <p>I have an array as following:</p>
  
  <pre><code>In [1]: x = array(['1.2', '2.3', '1.2.3'])
  </code></pre>
  
  <p>I want to test if each element in the array can be converted into numerical value. That is, a function: is_numeric(x) will return a True/False array as following:</p>
  
  <pre><code>In [2]: is_numeric(x)
  Out[2]: array([True, True, False])
  </code></pre>
  
  <p>How to do this?</p>