update the development status to beta

Author: basnijholt

README.md

@@ -15,7 +15,7 @@ With just a few lines of code you can evaluate functions on a computing cluster,
 Check out the `adaptive` [example notebook `learner.ipynb`](learner.ipynb) (or run it [live on Binder](https://mybinder.org/v2/gh/python-adaptive/adaptive/master?filepath=learner.ipynb)) to see examples of how to use `adaptive`.
 
 
-**WARNING: `adaptive` is still in an early alpha development stage**
+**WARNING: `adaptive` is still in a beta development stage**
 
 
 ## Implemented algorithms

setup.py

@@ -73,7 +73,7 @@ def make_release_tree(self, base_dir, files):
     author='Adaptive authors',
     license='BSD',
     classifiers=[
-        'Development Status :: 3 - Alpha',
+        'Development Status :: 4 - Beta',
         'License :: OSI Approved :: BSD License',
         'Intended Audience :: Science/Research',
         'Programming Language :: Python :: 3.6',