feat(ci): update cargo gen to 0.2.2

[ashleygwilliams]

cargo generate 0.2.1 introduce a bug that broke the relative paths undoc'd feature that this repo was leveraging. 0.2.2 fixes that bug and makes relative paths an official feature. this PR should force travis to update cargo-gen to 0.2.2 and should fix the ci breakage we've seen since 0.2.1.

[ashleygwilliams]

this is very interesting... passing on PR but not on push... have restarted the build to see. failing with "cannot find branch master" which is odd, since it's clearly being found in the PR test. will see!

[ashleygwilliams]

ok, with the debug statements i think im' getting closer, if travis is using a shallow clone on the push test, it won't have branches which is why this will fail.

on push:

0.00s$ git status
HEAD detached at 8f80944
nothing to commit, working tree clean
The command "git status" exited with 0.
0.10s$ cargo generate --git . --name testing
 Creating project called `testing`...
error: failed to find branch `master`
caused by: cannot locate local branch 'master'; class=Reference (4); code=NotFound (-3)
The command "cargo generate --git . --name testing" exited with 1.

[ashleygwilliams]

yup, detached head mode is what's biting us i believe: travis-ci/travis-ci#1701 (thanks to @drager for finding this!)

[fitzgen]

LGTM with potential sticky point below (but we should just merge and see if we run into that problem, I suppose)

[fitzgen]

If we get a cached cargo-generate, and therefore don't execute the updated cargo install command here, whill cargo install-update -a bump minor versions of an installed tool? If not, we may need to do two pushes: one that doesn't use any chached tool to force an install of 0.2.2, and then another to re-enable the use of cached tools. I think I've been bitten by this before. Not sure what the best way to deal with this is going forward.