Merge pull request #12 from ceeeeej/master

Added Chroma 62000P series DC Power Supply driver
Minor bugfix in ivi module
Point screenshot mapping to correct variable
Properly implement acquisition mode selection for Infiniium series scopes
Reorganize Agilent 8590E series drivers
Initial commit of Agilent 85644/5A tracking source driver
Update readme
Update authors file
Add output coupling setting to 85645A
Add missing file
Complete 85644/5A tracking source driver
Poll for YTM peak routine completion
Use write_raw instead of write for pyvisa interface
Use correct reset command
Rework rfsiggen module to use strings instead of ints for enumerated parameters
Add support for Agilent 8590A series spectrum analyzers
Add support for Agilent 8592L spectrum analyzer
Update readme
Fix screenshot code on 859xA series analyzers
Update supported instrument list for 8590 series base driver