Break plot.py in two separate files.

I have also removed all user prompts from the function that makes the
windows. These prompts hould now be inserted inside user's code.
Change name of module
Change module import.

Name of the `plot` module has changed to `plottools`.
Clean and add docstrings
Change module name.
Change name of module `spectra` to `spectools`.
Fix module call
Only apply radial velocity correction if observed spectrum is available
Delete `fort.11` before run and after test if exists.

Fix #9.
Remove unused `gdlwrapper` and `README`.
Move JSON class to `io` module.

Close #6
Merge pull request #11 from gabraganca/Clean-house

Clean house