aws-vault: Fix empty version string
aws-vault: Fix empty version string

- In issue 59, I noticed that `aws-vault --version` didn't output anything.
- This is because in the
  [Makefie](https://github.com/99designs/aws-vault/blob/master/Makefile#L2),
  it tries to do a `git describe --tags` which doesn't work because the
  tarball is not a Git repo, which results in:
  ```
  fatal: not a git repository (or any of the parent directories): .git
  go build -o aws-vault -ldflags="-X main.Version= -s -w" .
  ```
- Instead, set a `flags` variable that's passed into `go build` that
  includes the version string.
- This is, I think, preferable to setting this formula up to pull from a
  GitHub tag, as that needs more updating when a tag is released because
  `tag`s require `revision`s to pass the audit.

aws-vault: Add `revision 1` to rebuild the bottle

- The formula version hasn't had any changes, but the formula build step
  has. To rebuild the bottle and have people's bottled formulae upgrade
  seamlessly, bump the `revision`.

Fixes #59.
Closes #60.

Signed-off-by: Issy Long <b1c1d8736f20db3fb6c1c66bb1455ed43909f0d8@issyl0.co.uk>

LinuxbrewTestBot/homebrew-extra