Feature improve glyph inspector

This PR adds an arrow at the end of each glyph contour, like the `tx`utility of the [Adobe AFDKO](http://www.adobe.com/devnet/opentype/afdko.html) does.
Minor bug fixes too.

![b](https://cloud.githubusercontent.com/assets/2659709/2783854/ce941ab8-cb32-11e3-8b81-5179637ce910.png)