plotter_helper.plot_spectra now sets the datasets name as label.
Implemented plotter_heler.minmax_normalize

Normalize a spectrum in place by dividing it by the max(abs(y)).
After normalization all the y values are between [-1 and 1].
Added plotter_helper.integrate

Integrates a spectrum.

    Parameters
    ----------
    spectrum :
    inplace = False
        if the sepctrum should be modified in place or not

    Todo: what to do with errors?
Renamed spec to spectrum in plotter_helper.minmax_normalize
Changed default value of inplace to True in plotter_helper.integrate.

This seems more inline with the rest of the functions, which all work inplace by default.
Merge pull request #60 from ajasja/minmax

plotter_helper.minmax_normalize
Added plotter_helper.baseline_correct

    Substracts the baseline in place.
    Currently only a polynomial baseline is supported.

    Parameters
    ----------
    spectrum :
        spectrum-like object
    left_num = 100 :
        Number of point on the left side to take as baseline for fitting.
    right_num = 100 :
        Number of point on the right side to take as baseline for fitting.
    deg  = 3 :
        The degree of the polynomial.
Merge branch 'master' of https://github.com/SpectralGroup/spectraplotpy into integrate

RESOLVED Conflicts:
	spectraplotpy/plotter_helper.py
Merge pull request #61 from ajasja/integrate

Integrate
Merge branch 'master' of https://github.com/SpectralGroup/spectraplotpy into baseline

RESOVLED Conflicts:
	spectraplotpy/plotter_helper.py
	test/test_plotter_helper.py
Merge pull request #62 from ajasja/baseline

Added plotter_helper.baseline_correct