requirements-selftests: Add requirements from requirements-travis

Some packages from requirements-travis were not included in
requirements-selftests.
Signed-off-by: NLukáš Doktor <ldoktor@redhat.com>

requirements-selftests.txt

@@ -15,3 +15,9 @@ setuptools>=18.0.0
 six>=1.9.0
 # funcsigs
 funcsigs>=0.4
+# To run make check
+pep8>=1.6.2
+Pillow>=2.2.1
+snakefood>=1.4
+networkx>=1.9.1
+pygraphviz>=1.3rc2
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