Nmrsim

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Added
^^^^^
* nmrsim.Multiplet:
* :code:`w` attribute added (peak width at half height).
* nmrsim.SpinSystem:
* :code:`w` attribute added (peak width at half height).
* nmrsim.Spectrum:
* In-place addition modifies the Spectrum object in-place.
* :code:`vmin` and :code:`vmax` attributes added, to set spectral width.
* :code:`default_limits` method added, to reset spectral width to default.
* :code:`lineshape()` method added, to return lineshape data for the
spectrum.

Changed
^^^^^^^
* nmrsim.firstorder.multiplet now returns a *sorted* peaklist.

Fixed
^^^^^
* nmrsim.Spectum:
* Addition of Spectrum objects is commutative, and returns a new Spectrum
object.

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* Binaries for accelerating qm calculations packaged in distribution.

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Radical revisions (including a renaming of the project from "nmrtools" to "nmrsim") and migration to the
sametz/nmrsim repo on GitHub). Includes:

- New API
- Faster second-order calculations using sparse matrices and cached partial solutions
- High-level class-based API for convenient simulation and plotting of NMR spectra and components
- Jupyter notebooks demonstrating key API features and mathematical underpinnings

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Initial Commit