title: Pandas: DataFrame.quantile axis keyword does not work
body: <p>Any idea on why such a behavior?</p>
  
  <p><strong>Base data:</strong></p>
  
  <pre><code>In  [1]: tmc_sum.head(6)
  Out [1]:               1     2     3     8     9    10
           tmc                                          
           110+05759  7469  7243  7307  7347  7271  7132
           110P05759  7730  7432  7482  7559  7464  7305
           110+05095  7256  6784  6697  6646  6786  6530
           110P05095     0     0     0     0     0     0
           110+05096  6810  5226  5625  5035  5064  4734
           110P05096  6854  5041  5600  5308  5261  4747
  </code></pre>
  
  <p><strong>Prelude:</strong></p>
  
  <p>As per the <a href="http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.quantile.html" rel="nofollow">documentation of quantile</a>, this works correctly:</p>
  
  <pre><code>In  [2]: tmc_sum.quantile(0.05, axis=1)
  Out [2]: 1     3347.50
           2     1882.40
           3     1933.10
           8     1755.00
           9     1554.15
           10    1747.85
           dtype: float64
  </code></pre>
  
  <p>It correctly computes the 5th percentile by columns. (Note that there are more columns than the six printed above.)</p>
  
  <p><strong>Problem:</strong></p>
  
  <p>But this doesn't work as expected:</p>
  
  <pre><code>In  [3]: tmc_sum.quantile(0.05, axis=0)
  Out [3]: 1     3347.50
           2     1882.40
           3     1933.10
           8     1755.00
           9     1554.15
           10    1747.85
           dtype: float64
  </code></pre>
  
  <p>Which again computes by the column. Although, as per the documentation, it should compute by the row. So I tend to expect something like this:</p>
  
  <pre><code>In  [4]: tmc_sum.apply(lambda x: np.percentile(x, 0.05), axis=1).head(6)
  Out [4]: tmc
           110+05759    7132.2775
           110P05759    7305.3175
           110+05095    6530.2900
           110P05095       0.0000
           110+05096    4734.7525
           110P05096    4747.7350
  </code></pre>
  
  <p>Is this behavior expected and am I missing something, or is it a bug?</p>