Release 0.29.0

• Fix linting (5b8e333)
• Simplify gulp unit (1da89b3)
• Refactoring (dc5431c)
• Improve gulp-watch (25e1d60)
• Refactoring (99db554)
• Small refactoring (8cae425)
• Upgrade gulp-execa 0.6.0 -> 0.6.1 (7f05113)
• Upgrade gulp-execa 0.5.5 -> 0.6.0 (72e204f)