Migrating to GitHub Actions for CI

* GitHub Actions are setup to run for Mac, Linux, and Windows
* Linting only happens on Linux as we don't need to repeat this
  and it is complicated to install on both POSIX and windows
  systems easily
* In the doc.go file the word build was modified to b because the
  go toolchain on Windows (only windows) was considering the comment
  to be a malformed build comment. It was misdetecting it.
* Travis and Appveyor configuration have been removed

.github/workflows/test.yaml

@@ -0,0 +1,26 @@
+on: [push, pull_request]
+name: Test
+jobs:
+  test:
+    strategy:
+      matrix:
+        go-version: [1.12.x, 1.13.x]
+        platform: [ubuntu-latest, macos-latest, windows-latest]
+    runs-on: ${{ matrix.platform }}
+    steps:
+    - name: Install Go
+      uses: actions/setup-go@v1
+      with:
+        go-version: ${{ matrix.go-version }}
+    - name: Checkout code
+      uses: actions/checkout@v1
+    - name: Install golangci-lint
+      if: runner.os == 'Linux'
+      run: curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.sh | sh -s -- -b $(go env GOPATH)/bin v1.17.1
+    - name: Lint
+      if: runner.os == 'Linux'
+      run: $(go env GOPATH)/bin/golangci-lint run
+    - name: Test
+      env:
+        GO111MODULE: on
+      run: go test -cover .

doc.go

@@ -21,7 +21,7 @@ that can be sorted, compared, and used in constraints.
 When parsing a version an optional error can be returned if there is an issue
 parsing the version. For example,
 
-    v, err := semver.NewVersion("1.2.3-beta.1+build345")
+    v, err := semver.NewVersion("1.2.3-beta.1+b345")
 
 The version object has methods to get the parts of the version, compare it to
 other versions, convert the version back into a string, and get the original