Navigation backwards through opened buffers proceeds in order in which buffers were opened

[jakewvincent]

When navigating through files in nested directories, navigate backwards, and then navigate through nested directories along a different path, doesn't take you to last-opened, but to a file on the first path.

[jakewvincent]

Should be fixed with commit #d98c5fc. I implemented a pushdown stack in lua/mkdnflow/files.lua to help handle navigation in the expected way. The stack is a local variable defined in lua/mkdnflow/files.lua. Navigating from the current buffer using followPath() (mapped to by default) pushes the number of the buffer we just left onto the top of the buffer stack. Going back using goBack() (mapped to by default) takes us to the bufnr at the top of the stack, which is then immediately popped off the main stack and pushed onto a history stack. The history stack is currently not used for anything but I hope to eventually add a goForward() function that will be mapped to to bring back a buffer you just left via goBack().