Obstools

This release fixes a number of issues with the spectral calculations, plotting functions, channel descriptions and data handling. These changes appear mostly in the codebase, the scripts being largely un-touched. Changes include:
- Windowed Fourier transform is now calculated with `scipy.signal.stft`, for the QC steps and other spectral calculations. This ensures all windows are the same and avoids loading the `scipy.signal.spectrogram` and renders the `utils.sliding_windows` function obsolete.
- The full spectra are now kept in memory, as opposed to truncated spectra for the positive frequencies. This avoids potential bugs but increases the size of objects saved to disk.
- All example data are now provided in SAC format and no longer in .pkl files, which avoids `pickle` version conflicts.
- All scripts and functions load seismic data in `SAC` data format and no longer save the `EventStream` objects as .pkl files.
- All functions are free of `StDb` arguments, improving flexibility in the API
- API docstring and documentation have been updated

This new release fixes a number of details un-related with the core algorithms. Those changes appear mostly in the scripts. In particular, the changes include:

- Component name for the pressure channel in the downloaded .SAC files has been changed from '?HH' to '?DH' to follow proper convention. This has been changed in both `atacr_download_data` and `atacr_download_event` scripts.
- The script `atacr_correct_event` now automatically saves the corrected seismograms, both as a pickled `EventStream` object and as .SAC files, whose file name reflects the transfer function used (i.e., either the daily or station averaged transfer function (e.g., `day` vs `sta`), and the name of the transfer function applied (e.g., `ZP-21`)
- The online documentation has been thoroughly updated to reflect those changes.

On the to-do list, the package is missing a script to load "event" SAC files already present on disk, as opposed to downloading them on the fly. This will occur in tandem with a forthcoming package that manages seismic data archives.

This release fixes a number of minor bugs in the treatment of bad data, and provides more robust tests for cases where one or more components are missing. It also handles `StDb<=0.1.4`, but more work is required to upgrade to `StDb=0.2.0`.

Future developments will include:
- [ ] Handling of `StDb=0.2.0`
- [ ] Better handling of channels (e.g., if more than one `?DH` channel)
- [ ] Update documentation and resume CI using Travis
- [ ] Add modules (e.g., forward modelling compliance, etc.)

This is the first stable release of `OBStools`.

OBStools is a package containing Python tools for processing broadband ocean-bottom seismic (OBS) data. Current functionalities include removing vertical component noise from tilt and compliance effects. The code uses the StDb package for querying and building a station database and can be used through command-line scripts.