why are data types a good thing?
Fix for issue #149
miscellaneous tweaks from aringlis.
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.
changed caption for listing 1.
cleaning up citation styles
cleaning up citations
fix for listing 6
Merge pull request #156 from wafels/references

References
Merge pull request #154 from aringlis/misc_fixes

Miscellaneous tweaks from aringlis.