fix(package): update semver to version 7.1.2

Closes #19

Author: greenkeeper[bot]

package.json

@@ -25,7 +25,7 @@
   "homepage": "https://github.com/toxic-johann/git-prefix-tag#readme",
   "dependencies": {
     "core-js": "^3.0.0",
-    "semver": "^6.0.0",
+    "semver": "^7.1.2",
     "shelljs": "^0.8.1",
     "toxic-predicate-functions": "^0.2.3"
   },