fix(dependencies): fix #10

node-semver introduced the caret with v2.1.0
see isaacs/node-semver/commit/73b8fa4047f713e7a3e1c08a07139fea42c85a68
npm 1.3.7 is the first version of npm to require semver ~2.1.0
see npm/npm/commit/f369647b00d5f9599046396c1721ca49bf1689ff
chore(release): prepare v0.3.1