Test plotter_helper implemented.
Merge branch 'master' of https://github.com/odarbelaeze/spectraplotpy

Conflicts:
	spectraplotpy/__init__.py
Exceptions of the spectraplotpy library defined.
print eliminated
Reimplemented the ploting functionality, now you call call Spectrum.plot(plt, options) and the errors will be handled correctly.
Adding some more documentation.
Spoted a little error before hand.
Adding a little bit more documentation.
Merge branch 'master' of git://github.com/lidiabressan/spectraplotpy into lidiabressan-master
imprmented mock test for plot() and y_error_plot() in test_spectrum.py
Merge branch 'master' of https://github.com/odarbelaeze/spectraplotpy