explained the 'SJI' acronym
minor change
why are data types a good thing?
Merge pull request #145 from wafels/master

what does SJI mean?
Fixes for citations
added a draft of the reply to the referees.
Merge pull request #152 from aringlis/reply_referee2

Added a draft of the reply to the referees.
miscellaneous tweaks from aringlis.
Merge pull request #148 from ayshih/cite

Fixes for citations
Merge pull request #147 from wafels/2_edits

Why are data types a good thing?
included mission and instrument references for all the supported map sources
added in FITS reference
added in SSW reference
lightcurve data source references
spectra data source references
manual merge-in of master.
merging with master
small correction
fixed extra tab character
changed listing 1 to use demo file.