Some release tags aren't semver

[jamie-digital]

Issue description

The latest release (v1.3) isn't semver, so vgo breaks when trying to fetch v1.3.0, as the tag doesn't exist.

Example code

$ vgo get github.com/go-sql-driver/mysql@v1.3

Error log

vgo: finding github.com/go-sql-driver/mysql v1.3.0
vgo: github.com/go-sql-driver/mysql v1.3.0: unexpected status (https://api.github.com/repos/go-sql-driver/mysql/git/refs/tags/v1.3.0): 404 Not Found
vgo: finding github.com/go-sql-driver/mysql v1.3.0
vgo: github.com/go-sql-driver/mysql v1.3.0: unexpected status (https://api.github.com/repos/go-sql-driver/mysql/git/refs/tags/v1.3.0): 404 Not Found
vgo: unexpected status (https://api.github.com/repos/go-sql-driver/mysql/git/refs/tags/v1.3.0): 404 Not Found

Configuration

Driver version (or git SHA): v1.3

Go version: go version go1.10 darwin/amd64, go version go1.10 darwin/amd64 vgo:2018-02-20.1

Server version: N/A

Server OS: macOS 10.13.2

[jamie-digital]

This would be fixed by:

git tag -a v1.3.0 v1.3 -m "Tagged v1.3 as v1.3.0"

[julienschmidt]

Fixed. I preserved the old tags for backwards-compatibility.