Changed include_d to include_e for obs out if obs/obsd in.  Made informat and outformat required.  Fixed some comments.  And added a message when input is stdin.

deleted unused get_out_channels, cleaned up flow of convert_stream, and changed loop in check_stream to be more efficient.

cleaned up some code, added obsd as an input,  added check_stream to make certain the expected channels are coming in.

refactored to more cleanly use either files,  or stdin/stdout, added a write_string method to the iaga2002 factory, and some misc cleanup

Stream converter

added all the functions needed to convert to/from XYZ from HEDZ.  Changed get_mag_from_obs to use H,E,Z instead of H,D,Z.  Also added a function to go from HEZ to HEDZ, or any combo of E,D

Interfaces