Include tests/cases in sdist

Fixes #109

Author: naveen521kk

MANIFEST.in

@@ -1,8 +1,9 @@
 global-include *.pyx *.pxd
-recursive-include tests *.py *.ttf LICENSE.txt
+recursive-include tests *.py *.ttf LICENSE.txt *.svg
 recursive-include docs *.rst *.py make* _*/*
 prune docs/_build
 include *.md
 include *.txt
 include .coveragerc
 include LICENSE*
+prune *env*/