Added wvelocity file
Added file 'new_depths.py', which will eventually replace 'depths.py' in few commit cycles.
Adding new_depths.py

Merge branch 'master' of https://github.com/hetland/octant
In the processes of modifying the new octant depths.  Presently possibly unstable.
Drop-in replaced Scott Socolofsky's depths.py and roms.py using new_depths.py stretching, etc.
Major changes/refactoring to depths, including:
    Taking out the get_Vstretching_[1-4] and get_Vtransform_[1-2] functions from the (now)
    wrapper functions.

    Added depths wrapper functions that calculate the zrho, zw, or dz array in one command.

    Significant documenting and debugging.
Deleted new_depths.py after updating depths.py
- Modified wvelocity to a working version.
- Removed gridgen source code from setup.py
Merge branch 'master' of https://github.com/hetland/octant
Added python-gsw source to update old seawater package.
changes to vertical velocity -- retooled solution method.
fixed typo in isoslice
Merge branch 'master' of https://github.com/hetland/octant
Fixed the API for isoslice to match documentation (switched z and q)
Added w_velocity function, and some very basic value checking.  omegaHz and w calculations appear to be correct.
Changed import to gsw instead of sw (i.e., using new TEOS-10 equation of state)
Added hgrad to tools.py
Finalizing change from sw to python-gsw in setup.py.  Also, removed sw from repository.
Took out python-gsw.  Possibly include in external, but probably just include a link, and require it as a dependency.
Took out debugging print statements.