fixes #10 handle no newline issue

[chinglinwen]

test

func TestHost(t *testing.T) {
	hostsfile := "/tmp/hosts.txt"

	data := []byte("127.0.0.1 localhost")
	err := ioutil.WriteFile(hostsfile, data, 0644)
	if err != nil {
		t.Error("prepare test hosts file err", err)
		return
	}

	hosts, err = txeh.NewHosts(&txeh.HostsConfig{
		ReadFilePath:  hostsfile,
		WriteFilePath: hostsfile,
	})
	if err != nil {
		t.Error("create hosts err", err)
		return
	}
	spew.Dump("hosts: ", hosts)
	t.Logf("init: %q\n", hosts.RenderHostsFile())
}

origin

=== RUN   TestHost
(string) (len=7) "hosts: "
(*txeh.Hosts)(0xc00009a4e0)({
 Mutex: (sync.Mutex) {
  state: (int32) 0,
  sema: (uint32) 0
 },
 HostsConfig: (*txeh.HostsConfig)(0xc0000ba180)({
  ReadFilePath: (string) (len=14) "/tmp/hosts.txt",
  WriteFilePath: (string) (len=14) "/tmp/hosts.txt"
 }),
 hostFileLines: (txeh.HostFileLines) {
 }
})
    TestHost: hosts_test.go:37: init: ""
    TestHost: hosts_test.go:50: after add:  1.1.1.1          demo.com
        
    TestHost: hosts_test.go:61: after remove: 

after fixes

=== RUN   TestHost
(string) (len=7) "hosts: "
(*txeh.Hosts)(0xc00010c480)({
 Mutex: (sync.Mutex) {
  state: (int32) 0,
  sema: (uint32) 0
 },
 HostsConfig: (*txeh.HostsConfig)(0xc000122180)({
  ReadFilePath: (string) (len=14) "/tmp/hosts.txt",
  WriteFilePath: (string) (len=14) "/tmp/hosts.txt"
 }),
 hostFileLines: (txeh.HostFileLines) (len=1 cap=1) {
  (txeh.HostFileLine) {
   OriginalLineNum: (int) 0,
   LineType: (int) 30,
   Address: (string) (len=9) "127.0.0.1",
   Parts: ([]string) (len=2 cap=2) {
    (string) (len=9) "127.0.0.1",
    (string) (len=9) "localhost"
   },
   Hostnames: ([]string) (len=1 cap=1) {
    (string) (len=9) "localhost"
   },
   Raw: (string) (len=19) "127.0.0.1 localhost",
   Trimed: (string) (len=19) "127.0.0.1 localhost",
   Comment: (string) ""
  }
 }
})
    TestHost: hosts_test.go:37: init: "127.0.0.1        localhost\n"
    TestHost: hosts_test.go:50: after add:  127.0.0.1        localhost
        1.1.1.1          demo.com
        
    TestHost: hosts_test.go:61: after remove:  127.0.0.1        localhost