v0.9.19

TensorCrossInterpolation v0.9.19

Diff since v0.9.18

• Added an optional dims argument to sum(tt) that allows partial summation of TTs. If not all arguments are summed over, this returns a TensorTrain with the remaining legs.
• Changed the signature of integrate() to allow for different types in the integrand function's return type and domain.

Merged pull requests:

• Improve sum(tt) function (#72) (@rittermarc)
• In integrate(), separated type of integration domain (#73) (@rittermarc)
• bump version to 0.9.19 (#74) (@rittermarc)