Add build, tag for oniguruma, remove for mysql_go_regex, update README

README.md

@@ -41,16 +41,6 @@ To install it, run:
 go get gopkg.in/src-d/go-mysql-server.v0
 ```
 
-## Regular expression engine
-
-The **go-mysql-server** uses [oniguruma](github.com/kkos/oniguruma) as a default regular expression engine, so it's required to install the oniguruma first.
-For Linux (if you have the `apt-get` tool) or OSX (if you have `homebrew` tool) the easiest way is by command:
-```sh
-make oniguruma # on linux you may need `sudo`
-```
-
-If you want to use regex engine from go's standard library, you have to compile **go-mysql-server** with `--tags mysql_go_regex` argument.
-
 ## Documentation
 
 * [go-mysql-server godoc](https://godoc.org/github.com/src-d/go-mysql-server)

internal/regex/regex_go.go

@@ -1,5 +1,3 @@
-// +build mysql_go_regex
-
 package regex
 
 import (

internal/regex/regex_oniguruma.go

@@ -1,3 +1,5 @@
+// +build oniguruma
+
 package regex
 
 import (

internal/regex/regex_test.go

@@ -10,12 +10,12 @@ func dummy(s string) (Matcher, Disposer, error) { return nil, nil, nil }
 
 func getDefault() string {
 	for _, n := range Engines() {
-		if n == "go" {
+		if n == "oniguruma" {
 			return n
 		}
 	}
 
-	return "oniguruma"
+	return "go"
 }
 
 func TestRegistration(t *testing.T) {
@@ -33,9 +33,6 @@ func TestRegistration(t *testing.T) {
 	engines = Engines()
 	require.Len(engines, number)
 
-	err = Register("oniguruma", dummy)
-	require.Equal(true, ErrRegexAlreadyRegistered.Is(err))
-
 	err = Register("nil", dummy)
 	require.NoError(err)
 	require.Len(Engines(), number+1)