Fix gitRange for git+ssh for private git

[andreeib]

Reopened the previous pull request: #32
I haven't realized that git range works for hosted git like github.com but it doesn't for private git. Ex:

var npa = require("npm-package-arg");
try {
  var parsed = npa("git+ssh://git@github.com:npm/npm-package-arg.git#semver:~5.0.0");
  console.log(parsed.gitRange); // Works as expected: ~5.0.0
} catch (ex) {
  console.log(ex);
}
try {
  var parsed = npa("git+ssh://git@private.git.com:development/repositories.git#semver:~1.0.0");
  console.log(parsed.gitRange); // Dosen't work: undefined
} catch (ex) {
  console.log(ex);
}

[andreeib]

So it seems private git semver doesn't work when using colon separator:

> require('.')("git+ssh://git@github.com/npm/npm-package-arg.git#semver:^5.1.0").gitRange
'^5.1.0'
> require('.')("git+ssh://git@github.com:npm/npm-package-arg.git#semver:^5.1.0").gitRange
'^5.1.0'
> require('.')("git+ssh://git@notgithub.com/npm/npm-package-arg.git#semver:^5.1.0").gitRange
'^5.1.0'
> require('.')("git+ssh://git@notgithub.com:npm/npm-package-arg.git#semver:^5.1.0").gitRange
undefined

[zkat]

Nice! Yeah, it sounds like I missed a spot when the semver stuff was added and/or when scp specs were fixed last time around. Thank you!