Support for "~" version constraint operator for projects that use Semantic Versioning.

[jmalloc]

This PR provides support for a new version constraint operator specified with the tilde character.
It behaves similarly to the operator of the same name in npm.

For example, specifying the version constraint as ~1.2.0 is functionally equivalent to >=1.2.0,<2.0.0. If the package adheres to the semantic versioning specification then any version in this range is guaranteed to be compatible.

[travisbot]

This pull request passes (merged cd96664 into 65e95ed).

[Seldaek]

Cool, fixes #643 partially too. If you'd like to work on the rest of those issues it'd be great :)

[stof]

btw, the behavior described in this PR for ~1.2.0 does not match the behavior described in the issue.

[jmalloc]

@stof Are you referring to the fact that the normalised versions as used in the unit tests refer to ">1.1.999999.999999" instead of ">=1.2.0"? I did this for consistency with the existing wildcard operators, though now I fear I may have misunderstood the intent there.

[jmalloc]

@Seldaek I'll gladly take a look at #643, though I think I need to further my understanding of the normalised versions first :)

[ezzatron]

@stof The functionality in this PR actually makes more sense with its treatment of semver. I added a more detailed comment on #643 to explain my point further.

[stof]

@jmalloc no, I'm talking about the upper bound

[travisbot]

This pull request fails (merged e9d7125 into 65e95ed).

[travisbot]

This pull request fails (merged 5162b93 into 65e95ed).

[jmalloc]

Guys, I'll close this and re-open once all the features in #643 are complete.

[Seldaek]

As you wish, but if you don't have time to complete it please just reopen a PR with incomplete stuff, it's still better than nothing.

[jmalloc]

Oh, I'm definitely working on it - I have a few of the features complete, I just thought it was getting a bit noisy.

[Seldaek]

@jmalloc any news? :)