git urls can't handle a version range

[elijahsmith]

when specifying a git url for the package (or, probably but not tested, a custom package name) the version check fails if it is a range (eg ~0.0.1). This is because it's being validated with semver.valid() which is intended to validate a specific version string, not a range.

I would suggest that neither case should use semver.valid(), as it's an additional amount of validation that doesn't get applied to a "regular" version string.

[elijahsmith]

(if you like the suggestion that special validation for git url / custom package versions, I'd be happy to submit a PR for that...)

[mgol]

PR welcome. :) Be sure to add a test.