Fix incorrect use of Process::exit. This fixes open issue #244.

[jmax315]

🌈
Unlike the C library function exit(), Ruby's version takes a boolean,
not an integer. Added a spec to check the actual shell-level exit
value of a Thor script, and fixed calls to Process::exit.

[jmax315]

The build for 1.8.7 fails with problems in the webmock gem. As far as I can see, my change didn't cause these; does the current head build for 1.8.7 in CI correctly?

[lostapathy]

#583 fixes the travis error that shows up here.

[deivid-rodriguez]

@rafaelfranca What do you think about this? Backwards compatibility considerations about changing the default for this setting apart, this is fixing an actual bug, right?

[deivid-rodriguez]

Would it help if I rebase this PR and get it green? According to #244 (comment), even setting exit_on_failure? to true does not exit on failure. This PR seems like a feasible explanation and fix for that issue, and it's backwards compatible.

[deivid-rodriguez]

@rafaelfranca Since you're having a look at thor I'd like to politely ping you about this again.

[deivid-rodriguez]

Thanks! ❤️

The tests need to be skipped on 1.8.7 due to using spawn (or find another version that works ok on 1.8.7). Skipping seems easiest, no?

[rafaelfranca]

Yes. Skipping is fine

[deivid-rodriguez]

Ok, I'll open a separate PR to get it green!

[deivid-rodriguez]

Funny, while creating the PR to skip the tests on 1.8.7 I tried reverting the code changes in this PR and the specs still passed. So it seems that this PR didn't fix anything and the exit_on_failure? thing is actually working fine? The tests still seem good to catch future regressions so I guess it's ok.