Change from reshape2 to tidyr for pivots

[leppott]

Is your feature request related to a problem? Please describe.
Change references from reshape2 for melt and dcast to tidyr pivot_longer and pivot_wider

Describe the solution you'd like
Change package functions so can remove older package.

Describe alternatives you've considered
Could leave alone.

Additional context
last update to melt and dcast in 2018-09-27, v1.2.2.9020