leading underscore disables syntax highlighting for the line...

[busticated]

hi there -

thanks for the helpful lib! i ran into a minor thing - not sure if it's a bug or intentional behavior. what i'm seeing is that syntax highlighting is disabled when the jsx tagname starts w/ an underscore _ for example:

<_foo onClick={this.handleClick} /> // <== no hightlighting

<foo onClick={this.handleClick} /> // <== hightlighting works!

is that expected? if so, would you be interested in supporting an option to disable it (so leading underscores do not impact highlighting)?