Target association with relative distance measure

See merge request !181

Fix cost model incompatibility with pyfmmlib

Closes #130

See merge request !177

Eliminate separate conda requirements files

See merge request inducer/pytential!176

Improve the performance of test_cost_model_correctness() by caching

See merge request inducer/pytential!175

target-box-invariant TS evaluation results in ConstantOneQBXExpansionWrangler

TS: Fix variable initialization

See merge request inducer/pytential!174

The flag variables for which expansions to evaluate were not always
being initialized.

This changes the code to always initialize the flags.

Target-Specific QBX and Cost Model

Closes #5, #7, #1, #2 und #103

See merge request inducer/pytential!141

Prepare for caching in GeometryCollections

See merge request inducer/pytential!153