Bruges

- Fixed some bugs in v0.3.2, including a problem with non-integer indices in the windowed mean that `backus()` uses.
- Improved the time and depth conversion functions by adding the ability to return the new basis array (i.e. the new time or depth vector).

- Fixed a bug in `bruges.filters` that was returning the results from integer arrays as integers, giving incorrect results in those cases. Fixed tests.
- Reflectivity equations in `reflection` module now work on vectors, so you can use ndarrays for both the Vp, Vs, and rho values, and the theta values. They are about 10 times faster than running a loop over elements; the Zoeppritz is over 100 times faster. The results put the angles in the first dimension, so you can simply index in to get one offset.
- The Zoeppritz solutions and the Aki–Richards approximations now return the complex reflectivity and therefore show post-critical behaviour.
- New reflection coefficient series function, `reflection.reflectivity()` makes it easier to make offset reflectivities from logs.
- New acoustic reflection coefficient series function, `acoustic_reflectivity()`.
- Added `critical_angles()` and `reflection_phase()` functions to make it easier to compute the PP and PS critical angle(s), and to get the phase of a post-critical reflection.
- Improvements to `reflection` module docs.
- Deprecating `moving_avg_conv` and `moving_avg_fft`, and for now the function `moving_average()` will return the convolutional solution.
- Several more simple linear and non-linear filters in `bruges.filters`, including `median` (good for seismic horizons) and `mode` (good for waveform classification).
- You can no longer import 'all' from a module. This is a bad idea anyway, so I'm not calling it a breaking change.
- The wavelets `ricker()` and `sweep()` now return transposed matrices if you ask for a wavelet bank by providing several frequencies. This is so the wavelets are in the first dimension, so you get get one by simply indexing.
- The `ormsby()` wavelet now also works for a sequence of frequency tuples, returning a wavelet bank.
- Fixed a bug in the `sweep()` wavelet that caused a time shift in the sweep function. Also added the taper option to the `sweep()` wavelet.
- Added a `sinc()` wavelet, with a taper option to attenuate the sidelobes.
- Added `inverse_gardner`, and other density and velocity transforms, to `petrophysics`.
- Added `transform.v_rms()` (RMS velocity), `transform.v_avg()` (average velocity) and `transform.v_bac()` (naïve Backus average). These all operate in a 'cumulative' average-down-to sense, per Liner (2004), Elements of 3D Seismology.

- Repaired the `rockphysics.elastic_impedance()` function, which had various issues, including not applying normalization correctly and not working on vectors.

- **Breaking change:** `anisotropy.backus` now always returns `Vp0`, `Vs0`, and `rho`.
- Non-compatible change: `filters.wavelets.ricker` no longer normalizes the output, to avoid a problem with amplitude dependence on filter length.
- Functions returning tuples now return a `collections.namedtuple` so it's more obvious what you're getting back.
- New nonlinear filters (plus tests): `filters.snn()`, `filters.kuwahara()` and `filters.conservative()`.
- `sweep()` optionally returns time basis, like the other wavelets.
- `reflection.shuey()` optionally returns intercept and gradient instead of the terms. Set `return_gradient=True`.
- No more `shuey2()`, `shuey3()`, `bortfeld2()`, `bortfeld3()`. Use `shuey()` and `bortfeld()` instead.
- Zoeppritz calculation is now fully vectorized and 75% faster. Also added the full `scattering_matrix()` function to the list of available functions (it was previously a private function).
- Better tests of the `reflection` algorithms (lower numerical tolerance).
- Tidied up code.

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- Coordinate transformation for (x,y) and (inline, line).
- Fixed documentation.

- Fixes to elastic impedance.
- Returning rho from Backus average.
- Fixed Travis.