#6 indention cleanup, pretty-print option, bug on parsing objec

[linuxfun]

1. Add a pretty_print option, that indents object and array notation (this was my primary reason to start the work)
2. Add testcases for the pretty_printed version
3. Add lines method to StringGenerator, that reports the count of lines, that were read until that point (used to provide a better method to detect problems in json files)
4. Handle empty objects, which only contain whitespace
5. Convert all tabs to spaces (mostly spaces were used to indent)

Please contact me, if the patch has to be broken up into smaller chunks.

[linuxfun]