[BREAKING] copy*(): use ino to check identical paths

[manidlou]

...copy*() and long journey of dealing with lots of edge cases and trying to find a proper and yet simple approach to catch as many of those 🐛s as we can!

fix #565. Also possibly fix #546 as we don't use fs.readlink anymore to check the paths.

I guess it's breaking as for the case of symlinks, we throw error with descriptive message instead of silently return.

• use ino to check if src and dest are the same (Thanks to @TanninOne for bringing that idea). This is beyond checking just paths. Since fs.lstat stats the link itself not the actual file that it points to, we have to do an extra fs.stat to get the actual ino of both src and dest. This essentially relies on node's internal api to give us correct inos! This also catches the cases like when dest parent is a symlink that points to the parent of src! some 😲 stuff! (we used to only check src and dest themselves not their parents!)

• check isSrcSubdir when checking paths before start copying (achieved the same results with shorter code!)

[coveralls]

Coverage decreased (-0.6%) to 86.228% when pulling 456241a on copy-same-path into 3eceb91 on master.

[RyanZim]

LGTM