add scikit-optimize to dependencies

requirements.txt

@@ -21,5 +21,8 @@ networkx==1.11 # pyup: ignore
 tabulate==0.8.2
 coinmarketcap==5.0.3
 
+# Required for hyperopt
+scikit-optimize=0.5.2
+
 # Required for plotting data
 #plotly==2.7.0

setup.py

@@ -36,6 +36,7 @@ setup(name='freqtrade',
           'tabulate',
           'cachetools',
           'coinmarketcap',
+          'scikit-optimize',
       ],
       include_package_data=True,
       zip_safe=False,