fix: inc prerelease with numeric preid (#380)

Author: ntkme

Diff for: classes/semver.js

@@ -265,7 +265,7 @@ class SemVer {
         if (identifier) {
           // 1.2.0-beta.1 bumps to 1.2.0-beta.2,
           // 1.2.0-beta.fooblz or 1.2.0-beta bumps to 1.2.0-beta.0
-          if (this.prerelease[0] === identifier) {
+          if (compareIdentifiers(this.prerelease[0], identifier) === 0) {
             if (isNaN(this.prerelease[1])) {
               this.prerelease = [identifier, 0]
             }

Diff for: test/fixtures/increments.js

@@ -82,4 +82,9 @@ module.exports = [
   ['1.2.0-1', 'minor', '1.2.0', false, 'dev'],
   ['1.0.0-1', 'major', '1.0.0', 'dev'],
   ['1.2.3-dev.bar', 'prerelease', '1.2.3-dev.0', false, 'dev'],
+
+  ['1.2.3-0', 'prerelease', '1.2.3-1.0', false, '1'],
+  ['1.2.3-1.0', 'prerelease', '1.2.3-1.1', false, '1'],
+  ['1.2.3-1.1', 'prerelease', '1.2.3-1.2', false, '1'],
+  ['1.2.3-1.1', 'prerelease', '1.2.3-2.0', false, '2'],
 ]