Added possibility of getting tag name from different directory.

[PiotrSiatkowski]

Right now I can get branch name from different directory than my current working directory. Tag is often used alongside with the branch name, that's why it would be fine to have access to tag name from different repository as well.

In this PR I am passing directory string as a options.cwd parameter for child_proces.spawnSync method.
Method documentation is here

[kurttheviking]

@PiotrSiatkowski interesting; it looks like after merging in some prior PRs this change has some tests/conflicts that need to be resolved first

[andre-lima]

It seems to be due to @PiotrSiatkowski using ES6 syntax, that is not supported by Node 5 or lower.

Since these versions already reached End-of-Life ( https://github.com/nodejs/Release#release-schedule ) do you still want to support them @kurttheviking ?

[kurttheviking]

Yeah, I am open to refactoring in general and bumping the major. Then, just need to make it clear in the docs which Node version continues to be supported.