minor edits docu improvement
minor edits docu improvement

chdinh/mne-cpp,mne-tools/mne-cpp,LorenzE/mne-cpp,LorenzE/mne-cpp,chdinh/mne-cpp,LorenzE/mne-cpp,mne-tools/mne-cpp,chdinh/mne-cpp,mne-tools/mne-cpp,mne-tools/mne-cpp,LorenzE/mne-cpp,chdinh/mne-cpp,mne-tools/mne-cpp,mne-tools/mne-cpp,chdinh/mne-cpp,chdinh/mne-cpp