remove picotest as submodule
Squashed 'picotest/' content from commit d088dc1

git-subtree-dir: picotest
git-subtree-split: d088dc13a78338f440443eea043994e0bcea3dfc
Merge commit 'f36a7211a04daca0349429a1db619c5f70bc390a' as 'picotest'
switch from submodule to subtree (merge branch 'kazuho/picotest-as-subtree', fix #61)