removed one loop in the function period()
Fixed some indentation and define freqs array for future modifications
Fixed more identations
Changed the arguments of the period() function to 2 arrays and 1 optional harmonic int
changed deprecated pyfits to astropy.io.fits (as astrofits)
Cleared code, PEP-8 compatible, list comprehension
Commented deprecated implementation of harmonics (now on Milestones)
Added harmonic option
Fixed fits handling, erase bunch of unnecessary lines
added os to handle file extension, added blank lines to improve readability
Update README.md

changed pyfits to astropy
PEP 8 compliant corrections
Merge pull request #3 from evandromr/dev

Dev