gitignore: ignore _vim/.netrwhist

Signed-off-by: Guangliang Zhao <lucienchao@gmail.com>
bash: add RVM to $PATH

Signed-off-by: Guangliang Zhao <lucienchao@gmail.com>
vim: delete _vim/.netrwhist

Signed-off-by: Guangliang Zhao <lucienchao@gmail.com>