Constraint current implementation up to Go 1.8.

This commit is in preparation of the following commit which will add
support for Go 1.9.

It constraints the current implementation (meant for Go 1.8) so that
it will not be used in Go 1.9. A different implementation, located
elsewhere will be used for Go 1.9. See next commit for details.

.travis.yml

@@ -1,18 +1,15 @@
-language: go
 sudo: false
-
-matrix:
-  include:
-    - go: 1.2
-    - go: 1.3
-    - go: 1.4
-    - go: 1.5
-    - go: 1.6
-    - go: tip
-
+language: go
+go:
+  - 1.2
+  - 1.3
+  - 1.4
+  - 1.5
+  - 1.6
+  - 1.7
+  - 1.8
 install:
-  - # Skip
-
+  - # Skip.
 script:
   - go get -t -v ./...
   - diff -u <(echo -n) <(gofmt -d .)

go16.go → go16-18.go

@@ -1,4 +1,4 @@
-// +build go1.6
+// +build go1.6,!go1.9
 
 package gotool
 

match.go → match18.go

@@ -26,6 +26,8 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+// +build !go1.9
+
 package gotool
 
 import (

match_test.go → match18_test.go

@@ -26,6 +26,8 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+// +build !go1.9
+
 package gotool
 
 import (