Error handling

Issue #54 was implemented in this pull request.
Namely:
* REPL should not quit on any error.
* Correct file and position should be reported for parsing errors.
* Correct file and position should be reported for translation errors. Problematic term should be highlighted in console.
* Correct file and position should be reported for typing errors. Problematic term should be highlighted in console.

A cool result in action:

![screen shot 2013-10-29 at 12 21 25 am](https://f.cloud.github.com/assets/273180/1423648/8e639efa-400e-11e3-9e63-bcd9ea2f0148.png)