Initial commit of timing model sketch.
Merge branch 'scott'
timing_model: add parse/print Parameter methods, angle conversion.
timing_model: add explicit list of params as class variable.
timing_model: rename some functions
script for loading spice kernels.
spice tool box, not fully text yet
fixed DDDDD mistype
change spkzer(wrong function name) to spkezr(right one)
timing_model: start at defining how to compute delay/phase.
Merge branch 'jing'
Inserted some of Paul's TOA reading code.  Does not work yet.
Added tilde files
Added some basic information to the README including team and philosophy
Added a data directory
Added some ephemeris stuff
Added simple download script for ephemerides and Earth-rotation info
Added a couple more SPICE requirements
Added a couple of other required constants files
Improved the example for loading the kernels (including environment variable)