added check for successfully reading file, warning if it doesn't
added check for successfully reading file, warning if it doesn't

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