added vmin and vmax to display functional call
fixed crash, added ax and color map if an invalid what value is passed to display
bug fix, FITSOpticalElement if transmission=None, now creates array of ones(opd.shape) rather than shape= opd
correct axis called for phase plot of waveform
fixed case of use_fftw
merging with upstream
Merge remote-tracking branch 'upstream/master'

Conflicts:
	poppy/poppy_core.py
merging
Merge pull request #4 from douglase/master

Minor bug fixes and added adjustable waveform  intensity display range