Generation of homogeneous Poisson spike trains.
Test cases for homogeneous spike train generation
Remove unused and commented import.
Fixing pep8 warnings and errors.
Generation of inhomogeneous spike trains.
Merge branch 'feature/spikeTrainGen' into develop
Removed max_spikes arg from inhom. Poisson gen.

Does not make sense here as the resulting spike train will usually have
less spikes.
Victor Purpura's distance.

Needs some more documentation, though.
Documentation of VP distance function.
Restructuring tests for spike train metrics.

Extracting common tests to its own class.
Van Rossum distance.

Needs some more testing, documentation and maybe some refactoring.
Added test for van Rossum distance.
Rename pairwise_max_idx_of_smaller_item(...) ...

... to searchsorted_pairwise(...).
Shortening searchsorted_pairwise(...) code.
Documentation of van Rossum distance.
Documenting _searchsorted_pairwise
Correction of van Rossum distance.

- Square root was missing.
- Did not work with one spike train being empty.
Test spike train metrics with empty spike trains.
Normalization documentation for van Rossum dist.
Make normalization match the documentation.

(van Rossum distance)