Imexam

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- fixed a text error in the display_help() so that now the correct version loads the documentation
- Windows users can now install from source. The setup will ignore the cython and xpa necessary to build the DS9 interaction, and users will only be able to use the Ginga HTML5 window, they can also use the Imexamine() functions without any graphical interface.
- Documentation updates, mostly specific information for Windows users
- Added python 3.6 to the test matrix as well as apveyor for the windows build
- Updated XPA module to v2.1.18
- Made fits checker smarter to deal with older simple fits files where EXTEND is true but there are no extensions
- fixed bug in fits loader for ds9 multi-extension FITS files, made load_fits() prefer the extension specified in the key rather than the image name

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- Logging was updated to fix bugs as well allow for more user control of the log files. Additionally, most prints were moved to the stdout stream handler so that users could also shut off messages to the screen
- The imexamine class was updated so that analysis functions could be more easily called by external entities. This was primarily to support ginga plugins, and a new imexam plugin for ginga.
- A dictionary is now returned to the user when they request information on the active DS9 windows which are available.
- Tests updated to be consistent with new package logging
- Documentation and the jupyter examples updated
- Fixed bug with loading user specified fits extensions for both ginga and ds9

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- Unbinned radial plots were added, bins are still an available option
- documentation updates

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- Ginga viewer support for images in matplotlib and QT backend removed, but replaced with HTML5 canvas viewer which is faster and simpler for users to both use and install.
- replaced custom fits with astropy.modeling, enabling Gaussian2d, Gaussian1d, Moffat1D and MexicanHat1D fits for lines and centering
- General bug fixes and documentation updates, including example jupyter notebooks
- Updated the default title display on plots to use the image name or specify an array was used
- added astropy_helpers as a submodule
- made xpa a submodule
- if users pass an nddata object to view() without a data reference it assumes one, but you can always specify which extension
- added better user access function for changing plotting/function parameters used to make plots
- updated to Read The Docs new site name
- replaced ipython dependency in the docs build with jupyter
- removed local copy of doc build, referenced to RTD instead, users should make PDF copy for offline work
- added the ginga embed functionality so that users can choose to embed the viewing window inside the notebook

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- show with blocking deprecatedin matplotlib, changed the calls to pause
- added a radial profile plot under the r key, the curve of growth plot was moved to g

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- windows build change