Segy utility ready to use (psegy) + cookbook example

* Total refactoring of Caparicas code (almost re-done everything) but was a good start.
Mixed information from segy revision 1 document and segypy for modeling the tools.
Information of limitations of classes are in the doc string for the module.

* Short details:
The code is capable of reading and writing segy files (default headers can be used), can also make partial trace reading.
It has two main classes Segy and Trace of utilities for manipulation.
Other two classes derived from list containing header information SegyHD and SegyTH. 
The implementation take care of not loading the entire file (all traces) at once, so to avoid huge (giga sizes) files slowing down everything. 


* Added files
cookbook example : seismic_segy_io.py
cloudpspin635.segy : needed for cookbook example
psegy.py : segy utility module

Leo pode xingar a vontade rsrs mas please roda o cookbook example first. Ah sim tem que mudar ele de pasta, e nao sei se pode deixar esse segy, eu poderia criar um totalmente sintético.. Well waiting your orders

![sample_easy](https://f.cloud.github.com/assets/4503573/785301/71bc1118-ea7a-11e2-809f-410172d66e83.png)