Support `helm-gtags-find-tag-from-here` over TRAMP

`helm-gtags-find-tag-from-here` function invokes `global` with TRAMP filename, such as `global --result grep --from-here 100:/ssh:foo:/home/nksm/bar.c foo`

This commit fixes `helm-gtags-find-tag-from-here` to invoke `global` with remote filename.
Merge pull request #46 from gifnksm/patch-3

Support `helm-gtags-find-tag-from-here` over TRAMP