Update version number and add whats new for next release

Author: birgits

doc/whatsnew/v0-2-1.txt

@@ -0,0 +1,22 @@
+v0.2.1 ()
+++++++++++++++++++++++++++++++
+
+API changes
+#############
+
+
+Other changes
+#############
+
+
+Documentation
+#############
+
+Bug fixes 
+###########
+
+
+Contributors
+############
+
+

setup.py

@@ -7,7 +7,7 @@ def read(fname):
 
 
 setup(name='windpowerlib',
-      version='0.2.0',
+      version='0.2.1dev',
       description='Creating time series of wind power plants.',
       url='http://github.com/wind-python/windpowerlib',
       author='oemof developer group',

windpowerlib/__init__.py

@@ -1,6 +1,6 @@
 __copyright__ = "Copyright oemof developer group"
 __license__ = "GPLv3"
-__version__ = '0.2.0'
+__version__ = '0.2.1dev'
 
 from windpowerlib.wind_turbine import WindTurbine
 from windpowerlib.wind_farm import WindFarm