add hardware section that record issues with common hardware
Reorganize sections under Hardware

Some reorganization of sections under Hardware.
Major sections includes:
1. Common: describes common stuff
2. Computation: describes computation unit such as nuc, odroid...
3. Robots: robots, obviously
4. Sensors: bluefox, imu, lidar, these can be links to seperate
driver repos and details can be described there
Fix some grammar mistakes
Merge pull request #8 from KumarRobotics/feature/add-hardware

add hardware section that record issues with common hardware