Revert to older Travis-CI testing framework so we can separate testing from conda dev builds.
Merge pull request #533 from jchodera/revert-travis-ci

Revert to older Travis-CI testing framework to separate testing from conda dev builds
Merge pull request #535 from peastman/master

Fixed bug when running on a CPU device
- Some minor cleanups and simplifications in the Amber prmtop parser.
- Convert coordinates, velocities, and box vectors into Vec3 objects to avoid a
  subtle bug in the units module with respect to silently modifying mutable
  collections in-place when converting to a new set of units.
Merge pull request #536 from swails/fix_inpcrd_units

Convert AmberInpcrdFile data structures from lists to Vec3
Merge pull request #538 from peastman/master

Fixed a bug in unit conversion for sequences
Add an explicit (shallow) copy constructor for CustomNonbondedForce. This fixes
segfaults when you use the long-range dispersion correction with the
CustomNonbondedForce if the force uses TabulatedFunction objects. Basically, it
prevents the copy from taking ownership (and deleting) the functions in its
destructor.

The use cases for CustomNonbondedForce copying currently is to recompute the
long-range prefactor if the parameters change (so the CustomNonbondedForceImpl
kernels need a copy of the Force object). Doing a full (deep) copy would be a
bit slower (although would only need to be paid once for each
CustomNonbondedForce object being used).
Switch to a deep copy on the tabulated functions in CustomNonbondedForce. This
necessitated creating a Copy method to do that on TabulatedFunction classes.
- Make the TabulatedFunction::Copy method a pure virtual.
- Don't make a Copy method on FunctionInfo
- Have the Copy() methods on the TabulatedFunction subclasses return a pointer
Get rid of vestigial variable.
Add a comment about updating the copy constructor if the implementation details
are changed for CustomNonbondedForce.
Add 12-6-4 potential support.
Add a test for the 12-6-4 potential.
Merge pull request #539 from swails/fix_customnonbondedforce_segfault

Fix customnonbondedforce segfault
Make sure inpcrd files are copied to the build directory.
Merge pull request #532 from swails/lj1264

Support new 12-6-4 potential
Merge pull request #541 from peastman/master

Fixed error in DrudeForce::updateParametersInContext()