Pyuvsim

Added
- A parallelized counter that can track progress across all ranks.
- shared memory broadcast, which will create a shared memory window for a given object on each node
- Function to generate UVData object from keywords, optionally saving config files.
- Optionally, can skip having telescope_config file if there is no beam list.

Changed
- UVBeam frequency interpolation is cubic spline by default, not linear.
- Tasks are split over time, frequency, and baseline only (in that order).
- Tasks are split over the source axis if the estimated memory footprint exceeds available resources.
- The source class is replaced with SkyModel, which supports vectorized coordinate transformation and beam interpolation.

Fixed
- MPI.Init -> MPI.Init_thread(), for threaded applications.
- Progress steps now update in real time, accurately reflecting job progress.
- Analytic visibility calculation tests now also check analytic beams.
- Analytic beams are redefined so that off-diagonal Jones matrix terms are zero.
- parameter dicts are not modified by functions using them.

Deprecated
- Coarse horizon cuts are no longer performed. Should be restored in a future version.

Added
- More detailed comparison to other simulators in the documentation.
- Option to convert analytic beams from efield to pstokes
- Enabled Gaussian beams to be defined with power law widths.
- Enabled Gaussian beams to be defined from antenna diameter and have chromaticity
- Checking the beam kernel width makes sense for Airy beams

Changed
- Pending deprecation of gaussian beams defined from sigma parameter

Fixed
- pip installation instructions

Added
- Support for only simulating one baseline per redundant group

Fixed
- Using the correct Bessel function in the definition of the Airy beam

Added
- Support for miriad and uvh5 output
- stdout printing explicitly disabled for non-root ranks
- Flux cut options with source catalogs
- Coarse horizon cut for reduced computational load.
- Selection keys in obsparam files (valid options for UVData.select)
- New batch scripts for profiling jobs on a SLURM-managed cluster, and plotting the results.

Changed
- Rename write_uvfits to write_uvdata
- Fixed memory overload bug due to local task indices creation step.
- Moved parameter simulation functions from wrapper to uvsim
- MPI3 enabled in travis.
- Line profiling may be done by running `pyuvsim.profiling.set_profiler`.
- Which functions to profile is set by listing them by name, instead of by function decorators.
- Improved test coverage

Deprecated
- Simulation directly off of uvfits files.

Changed
- Tasks are generated in place on each rank.
- UVEngines are reused by the worker loops.
- Alt/Az quantities are only recalculated for each source when the time changes.
- Use `reuse_splines` option on UVBeams to reduce interpolation time.
- Beams are scattered as strings, not objects.