Add --reinstall argument to the install option

[iddm]

The --reinstall option simply uninstalls the package before installing
it so the user need not run uninstall and then install. This also updates the
package since install always look for a new version.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @alexcrichton (or someone else) soon.

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[iddm]

Tired of doing the same work (uninstall & install) :)
#2082
https://stackoverflow.com/questions/48438783/is-there-a-way-to-update-a-binary-package

[sfackler]

How is this different from cargo install --force?

[iddm]

@sfackler Good question. I have told by many people that the --force and uninstall and then install is different. Is not that true?

[sfackler]

How were they claiming it was different?

[iddm]

@sfackler No way. I should go and sleep. I read an old answer on the stackoverflow yesterday which told that there was no such a way and then the other guy told the same but it seems he did not know the answer himself. Sorry for bothering :)