update version number for 2.5.5 release

Author: C.A.P. Linssen

setup.py

@@ -27,7 +27,7 @@
 In addition to continuous dynamics, discrete events can be used to model instantaneous changes in system state, such as a neuronal action potential. These can be generated by the system under test as well as applied as external stimuli, making ODE-toolbox particularly well-suited for applications in computational neuroscience."""
 
 setup(name="odetoolbox",
-      version="2.5.4-post-dev",
+      version="2.5.5",
       author="The NEST Initiative",
       classifiers=['Development Status :: 4 - Beta',
                    'Environment :: Console',