Denis Erkal's mass for TwoPowerSphericalPotential
fix potential evaluation for general case of TwoPowerSphericalPotential, Integer doesn't work now
more interesting default params for TwoPower, so the tests do something interesting
start on test module for potentials
more interesting default p for Cosmphi for tests
more interesting default p for elliptical disk for tests
more interesting default p for Lopsided disk for tests
nose test that the derivative of the potential is minus the force
More reasonable cut-off as default for the potential tests
add tests of the phi force
better z2deriv for spherical potential
test z2deriv
avoid NaN in Rzderiv of Miyamoto-Nagai potential
test Rzderiv
add phi2deriv for planarPotentials
add 2nd azimuthal derivative test
add plotting of effective potential
allow plotting and calculating range to be specified independently in plotPotential
more reasonable default Miyamoto-Nagai parameters for tests
default values for FlattenedPowerPotential that make the density non-zero