Nexpy

* Fixes a long-standing PyQt issue with Mac OS X menus being unresponsive without switching to and from another application.

* Detects changes in an open file made by an external process. The file's lock icon is colored red, indicating that the file should be reloaded.
* Adds the option to clear stale file locks when it prevents operations on an open file.
* Adds a menu item to export one-dimensional data to a multicolumn ASCII file.
* Adds the option to add a smooth interpolation to one-dimensional point plots.
* Improves the dialog to customize plots, which allows the choice of open or closed symbols, adds smooth lines to the legends, and makes legend labels persistent between plots.
* Adds autocompletion of NeXus group dictionary items.
* Gives the option of omitting an NXentry group when creating a new workspace.
* Adds the use of a configuration file, ~/.nexpy/config.py, to customize the startup of a new NeXpy session.
* Disables menu items that are incompatible with the selected group or field in the tree view.
* Adds information about h5py options, such as compression and shuffle filters, when viewing a field.
* Remove restriction on the minimum signal value in plots on a log scale.
* Improves handling of malformed plot axes.
* Fixes a bug when adding groups to a root group using the 'Add Data' dialog.
* Installs Travis-CI checks on Github.

* Uses tabbed windows for the Projection, Limit, and Customize panels.
* Enhances the Limit panel (accessible using 'Window/Change Plot Limits') to allow the complete configuration of a plot (axes, axis limits, signal limits, window size, log scale, aspect ratio, color map, interpolation, and skew angle) to be copied from one window to another, to facilitate comparisons between the two.
* Adds a Help menu link to an online Jupyter Notebook tutorial about the Python NeXus API.
* Harmonizes window closings. `Ctrl+W` will close the currently active window, except with tabbed interfaces, where it closes the currently active tab.
* Make shapes added to the plot from the shell, using `plotview.rectangle(...)`, `plotview.circle(...)`, etc., draggable and resizable.
* Adds an option to the Projection panel to plot one-dimensional projections with lines.
* Adds `.nxspe` to the list of default file extensions.
* Fixes a bug in selecting default data to plot from parent groups.
* Fixes the colorbar normalization in Matplotlib 3.1.0.
* Fixes the use of pyplot commands from the shell in Matplotlib 3.1.0, e.g., `plt.figure()`. NeXpy and pyplot windows now coexist independently of each other.
* Fixes a bug displaying legends in Matplotlib 3.
* Improves Python 2 compatibility. Note that this is the last major version that will support Python 2. From v0.12.0, only Python 3 will be supported.

* There is a bug in the latest versions of ipykernel (>v5.0.0), which causes the IPython shell to stop working after any exception is triggered. This release overrides the ipykernel function that contains the bug.

* Adds an `Open Directory` menu item to load a complete directory of NeXus files.
* Adds an `Open Image` menu item to import images. It uses the Fabio library for importing images in TIFF and CBF files and the Pillow library for importing JPEG, PNG, and GIF files.
* Harmonizes the shutdown procedure when initiated by closing the main window, typing `exit` in the shell, or invoking the `Quit` menu, making it more compatible with different operating systems.
* Plots boolean NXfields as int8 arrays to prevent Numpy warnings.
* Adds a number of convenience functions to the BaseDialog for use in plugin modules, including support for threads.
* Adds keyboard shortcut 'F' to flip the y-axis.
* Changes the keyboard shortcut for unlocking NeXus files to `Ctrl+Shift+U` on non-Mac systems to ensure that `Ctrl+U` can still be used in the shell. On Macs, there is no clash because `Ctrl+U` is mapped onto `Cmd+U`.
* Utilizes the lmfit module for fitting GridParameters.
* Improves compatibility with changes to the ColorBar in Matplotlib v3.
* Fixes a bug causing the highlights of tree items to be split when opening a group.
* Fixes a bug when previous interpolation settings are not available in subsequent plots.

* Updates nexusformat requirement to v0.4.17, which fixes a number of important bugs.
* Fixes a bug with setting the full path in plot legends.
* Fixes a bug with fitting data, in which the x-axis is stored as bin boundaries.