Option to mask streamlines

From pr: #86
Commits from: @lheagy
Review from: @thast, @rowanc1

add the ability to mask streamlines if the amplitude is below a given threshold (stream_threshold).

add IO functionalities to write DCIP2D mesh and models

From pr #84

• commits from @thast
• review from @lheagy

add IO functionalities to write DCIP2D mesh and models

• the MeshIO functions writeUBC and writeModelUBC are now compatible with 2D meshes and models.

• We now make sure that mesh and model get saved at the same place by giving the option to specify the folder outside of the filename (before the folder was given by the dict.keys, not very practical)

• The upgrade is backward compatible

h_gridded

New mesh property: h_gridded

• From pr #77
• commits from: @dccowan, @lheagy
• review from: @lheagy, @rowanc1

This function works for TensorMesh and TreeMesh types. Much like gridCC, h_gridded returns [hx,hy,hz] as a nCxdim numpy array. This function is important for multiple potential fields problems (Mag, VRM, grav) in 3D.

dependency management

Changes from #80

• properties >=0.3.6b0 is required for running this version of discretize
• properties and vectormath are installed separately so versions can be managed explicitly

properties and serialization

Implement properties in discretize

• from pr #70
• commits from: @lheagy, reviews from: @rowanc1, @fwkoch

Use properties to define the properties of a class that are necessary to completely define the object. This allows us to serialize, save and load meshes (also copy!)

Related issues and discussion

• private properties: seequent/properties#191
• arrays with arbitrary shape: seequent/properties#192

implement properties in discretize

Implement properties in discretize

• from pr #70
• commits from: @lheagy, reviews from: @rowanc1, @fwkoch

Use properties to define the properties of a class that are necessary to completely define the object. This allows us to serialize, save and load meshes (also copy!)

Related issues and discussion

• private properties: seequent/properties#191
• arrays with arbitrary shape: seequent/properties#192

Extract Core Mesh Util

originally from pr #67, with commits from @thast, @lheagy, review from @rowanc1

• port over fixes that were made in SimPEG extract core mesh
• add testing on the 1D and 2D extract core mesh util

cleanup imports

Clean up Tree Mesh imports

• pr #63. commits from @lheagy, review from @rowanc1

Try / except the import of TreeMesh in Tests. This should remove all dependence that the cython code be properly set up in order to import discretize (continues to be an issue on windows...)

numpy upgrades, IO for UBC meshes

IO: UBC meshes

contributions from: @thast, @micmitch, review from @lheagy
from pr #54

• discretize.TensorMesh.readUBC is now a wrapper for loading either 2D or 3D mesh
• discretize.TensorMesh.readUBC can take care of recognizing if the file is a 2D or 3D UBC mesh, or it can be an input given by the user (arg: meshdim)
• the original functions are now hidden class function under discretize.TensorMesh._readUBC_3DMesh and discretize.TensorMesh._readUBC_2DMesh
• comments in UBC files are assumed to be marked with "!" in front

utils.Zero: Numpy upgrades

contributions from: @lheagy, review and comments from @rowanc1, @jcapriot
from pr #61

• Updates to Identity() and Zero() so that they are consistent with numpy upgrades in numpy=1.13.0 (https://github.com/charris/numpy/blob/master/doc/source/reference/arrays.classes.rst)
• use scipy.sparse.dia_matrix for spzeros (closed #60)

Install Cleanup

Noteworthy Changes

• use a try / except pair when importing the TreeMesh in the main init
• have efficiency warnings state that the user should use python setup.py install if cython code is not there in the interp utils
• use a try / except in the setup.py when importing numpy to tell the user to install numpy if it fails.

Minor Changes

• add codacy, quantified code badges to docs
• pinning to sphinx==1.5.6 for sphinx gallery to build. This is stated in #57 and will be released when upstream changes are made