Fix a name clash of click_common and the argument "command"

[syssi]

of device methods (Closes: #325)

[syssi]

@yawor Is a rename of the variable a proper approach? A leading underscore looks weird.

[coveralls]

Coverage remained the same at 72.353% when pulling ef34c29 on syssi:feature/miiocli-command-name-clash into a639b12 on rytilahti:master.

[yawor]

Rename either that or the "command" argument in chuangmi_ir to "ir_command" or something like that.
The arg name in the command_callback is used strictly internally, so this is probably a better way, as it doesn't really affect anything.

[syssi]

There are some more methods with a parameter called "command". That's the cause, why I choose this approach.