Closes #423 total_irrad docstring (#425)

* Fix total_irrad docstring

* Correct formatting in irradiance.py; update whatsnew.rst

* Update irradiance.py

Author: cwhanse

docs/sphinx/source/whatsnew/v0.5.2.rst

@@ -16,6 +16,7 @@ Bug fixes
 * fixed redeclaration of test_simplified_solis_series_elevation (:issue:`387`)
 * physicaliam now returns a Series if called with a Series as an
   argument. (:issue:`397`)
+* corrected docstring for irradiance.total_irrad (:issue: '423')
 
 Documentation
 ~~~~~~~~~~~~~

pvlib/irradiance.py

@@ -294,13 +294,20 @@ def total_irrad(surface_tilt, surface_azimuth,
                 model='isotropic',
                 model_perez='allsitescomposite1990', **kwargs):
     r"""
-    Determine diffuse irradiance from the sky on a tilted surface.
+    Determine total in-plane irradiance and its beam, sky diffuse and ground
+    reflected components, using the specified sky diffuse irradiance model.
 
     .. math::
 
-       I_{tot} = I_{beam} + I_{sky} + I_{ground}
+       I_{tot} = I_{beam} + I_{sky diffuse} + I_{ground}
 
-    See the transposition function documentation for details.
+    Sky diffuse models include:
+        * isotropic (default)
+        * klucher
+        * haydavies
+        * reindl
+        * king
+        * perez
 
     Parameters
     ----------
@@ -333,8 +340,8 @@ def total_irrad(surface_tilt, surface_azimuth,
 
     Returns
     -------
-    irradiance : OrderedDict or DataFrame
-        Contains keys/columns ``'poa_global', 'poa_direct', 'poa_diffuse', 
+    total_irrad : OrderedDict or DataFrame
+        Contains keys/columns ``'poa_global', 'poa_direct', 'poa_diffuse',
         'poa_sky_diffuse', 'poa_ground_diffuse'``.
     """
 
@@ -1326,8 +1333,8 @@ def dirindex(ghi, ghi_clearsky, dni_clearsky, zenith, times, pressure=101325.,
     Determine DNI from GHI using the DIRINDEX model, which is a modification of
     the DIRINT model with information from a clear sky model.
 
-    DIRINDEX [1] improves upon the DIRINT model by taking into account turbidity
-    when used with the Ineichen clear sky model results.
+    DIRINDEX [1] improves upon the DIRINT model by taking into account 
+    turbidity when used with the Ineichen clear sky model results.
 
     Parameters
     ----------
@@ -1389,7 +1396,8 @@ def dirindex(ghi, ghi_clearsky, dni_clearsky, zenith, times, pressure=101325.,
                         use_delta_kt_prime=use_delta_kt_prime,
                         temp_dew=temp_dew)
 
-    dni_dirint_clearsky = dirint(ghi_clearsky, zenith, times, pressure=pressure,
+    dni_dirint_clearsky = dirint(ghi_clearsky, zenith, times, 
+                                 pressure=pressure,
                                  use_delta_kt_prime=use_delta_kt_prime,
                                  temp_dew=temp_dew)