Xapres

Fixed

- merge changes in upstream fork of bas-apres (commit in that sub-module: [59dbd62](https://github.com/jkingslake/bas-apres/pull/2/commits/59dbd6211274b2260cba6a57020358f57e6972b6))

Changed

- Update load.py to using bas-apres instead of our own loading code

Added

- Add many new tests

Removed

- Remove ApRES_plot.py

Fixed

- move chirp_time dtype correction [8c9a5fe](https://github.com/ldeo-glaciology/xapres/pull/67/commits/8c9a5fe49852fac55f0b94622101ce66fd20941b)
- deal with case when nattenuators is different in different bursts in attended lod [bf3028b](https://github.com/ldeo-glaciology/xapres/pull/67/commits/bf3028b8dd80477c26bef68321dc840245e424c1)
- fix bug in attended load using from_dats.load() [8c9a5fe](https://github.com/ldeo-glaciology/xapres/pull/67/commits/8c9a5fe49852fac55f0b94622101ce66fd20941b)
- fix bug aligning profiles in computeProfile [44487cc](https://github.com/ldeo-glaciology/xapres/pull/67/commits/44487cc7ec1513ebf77f0e8fa160056ff235e136)

Added

- Add the displacement_timeseries method in utils
- Add the compute_displacement method in utils
- Add a number of methods that displacement_timeseries and compute_displacement call in utils
- Add the computeProfile method in utils
- Add documentation hosted on github pages
- Add material to usingXApRES.ipynb (now superseded by the documentation)