Doc string for filter_by_type
Playing with imports in __init__.py
- There is coded (commented out) that will loop through all files in the directory and import them all
Update to __init__.py
Merge branch 'feature/NewPNM' of https://github.com/PMEAL/OpenPNM into feature/NewPNM
Minor improvement to the default name generation...less random numbers and prepends subclass rather than module.
Add a BasePhysics subclass that uses a basic set of pore and throat scale models
Added InvasionPercolationForImbibition (written by Jon Ellis, ip_demo will run it)

Changed default loglevel to 30! Personal preference, feel free to override this decision.

Gave Air capillary properties

Updated documentation on IP algorithm
Merge branch 'feature/NewPNM' of https://github.com/PMEAL/OpenPNM into feature/NewPNM
Deleted old Vtp and __VTK__ files.
Renamed __Vtp__.py as __VTK__.py
Renamed Vtp_class as VTK
Updated run_script and ip_demo to behave properly
Added a BasePhyscis subclass
- It's still a bit bare, but it's started
- Interesting problem...it needs to check for the existence of the required variables for each physics and only add the right ones to the object
Started adding a Tortuosity algorithm
- This uses Djikstra's shortest path search and finds the distance between any pore and all others.
- Still in-progress...I'm not sure what weighting to apply to edges
Merge branch 'develop' of https://github.com/PMEAL/OpenPNM into develop
improved the toc function to return the time as well as print it.  added a 'quiet' argument as well to avoid printing.
Refinements to Tortuosity
- It returns the ratio of network distance to crow-flies distance between every two pores
- It now has a 'estimate_time' method that works quite well
OP now returns 'occupancy' as a float
- this accommodates late pore filling
- also plays nice with labels vs props methods
Fixed OP to now return float values for 'occupancy' for BOTH fluids
Added final touches to Tortuosity
- If no fluid is sent, it get dry tortuosity between every pair of pores
- If a fluid IS sent, it will apply the 'throat.occupancy' to the connectivity matrix, to get the tortuosity in that phase.
- This method returns as a 2D Nt x Nt matrix that can be nicely visualized with plt.imshow
Fixed minor bug in props.  If N pores are sent, then it now returns the value for all N pores for scalar properties.
Fixed bug in Tortuosity...it now returns the Leff/L between all sets of pores
- I guess to be useful, this alg should take the returned array and calculate some overall property for the network.
Numerous docstring updates to Tools