Allow comments in .terraform-version file

[OJFord]

Using syntax:

# this whole line is a comment
1.2.3
# this is also a comment

but not inline comments.

Closes #283

[jgrumboe]

Hi @OJFord
I would vote against comments as there are probably also other tools relying on this file in the existing format.
And there’s also an open issue at the setup-terraform action which could also rely on the file.
hashicorp/setup-terraform#208

Additionally, I checked .ruby-version and .node-version and both also don't support comments as that supports the simple "cat" use case like rbenv use $(cat .ruby-version) for example.

[mputilin]

Useful feature. Please merge.

[Zordrak]

It does seem that the general consensus, especially in a wider community sense, with different tools consolidating on common configuration files, that while this might sometimes be handy, it's likely to be more troublesome than the minor value it would add.