fix(blame): Fix recursive blame
fix(blame): Fix recursive blame

* avoid to treat commit as invalid filepath like following
  * `TIGRC_USER=/tmp/vGPgeSJ/5 tig blame /home/iberianpig/.ghq/github.com/iberianpig/tig-explorer.vim/22ebd739e28b31016df6eca8cfc073fd9a323192 +19 -- README.md`
* fix to following
  * `TIGRC_USER=/tmp/vGPgeSJ/5 tig blame 22ebd739e28b31016df6eca8cfc073fd9a323192 +19 -- README.md`

iberianpig/tig-explorer.vim