cmd/schemagen: refactoring

- Replace log.Faltal with error wrapping in schemagen func
- Simplify tests, use temp dir and ioutil functions, remove boilerplate code
- In test use schemagen keyspace to avoid name conflict with examples
- Change template

cmd/schemagen/camelize.go

@@ -0,0 +1,43 @@
+// Copyright (C) 2017 ScyllaDB
+// Use of this source code is governed by a ALv2-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"fmt"
+	"unicode"
+)
+
+func camelize(s string) string {
+	buf := []byte(s)
+	out := make([]byte, 0, len(buf))
+	underscoreSeen := false
+
+	l := len(buf)
+	for i := 0; i < l; i++ {
+		if !(allowedBindRune(buf[i]) || buf[i] == '_') {
+			panic(fmt.Sprint("not allowed name ", s))
+		}
+
+		b := rune(buf[i])
+
+		if b == '_' {
+			underscoreSeen = true
+			continue
+		}
+
+		if (i == 0 || underscoreSeen) && unicode.IsLower(b) {
+			b = unicode.ToUpper(b)
+			underscoreSeen = false
+		}
+
+		out = append(out, byte(b))
+	}
+
+	return string(out)
+}
+
+func allowedBindRune(b byte) bool {
+	return (b >= 'a' && b <= 'z') || (b >= 'A' && b <= 'Z') || (b >= '0' && b <= '9')
+}