ignore vim swap files
rename head/foot to .txt

The better to not confuse Visual Studio.

Fix #90
Revert "^0.x.y always equivalent to =0.x.y"

This reverts commit 3f676f510b311f63bc1dac2f92174f589bc5a14b.
support SemVer objects in cmp function
parse version in Range.test
new v4 range prerelease behavior

Simplify range expansions to remove -0 everywhere.

Only allow -prerelease versions that have a -prerelease tag on a version
in the range with the same exact X.Y.Z tuple.
Correct behavior of Caret operator with prerelease tag and 0.0.x version
Handle build properly when -pre is not specified
document version 4 range semantics

Document partial versions in hyphen ranges (Fix #76)