bench 1.1.0

New features

• New bench_process_memory() function, to return the current and maximum
  memory used by the current process. This uses system functions to track
  memory, so can measure memory outside of R's GC heap.

• New workout_expressions() function, a low-level function to workout a list
  of expressions, like those obtained via parse() from a file.

• mark() gains a memory argument to control if it records memory
  allocations, set memory = FALSE to disable recording memory allocations,
  which can be helpful when trying to benchmark long pieces of code with many
  allocations (#62).

Minor improvements and fixes

• mark() now permits empty arguments, e.g. accidental trailing commas (#61).

• mark() now errors correctly when the expressions deparsed length is
  different.

• bench_expr objects now work better with the upcoming versions of tibble and
  vctrs (@romainfrancois, #64)

• autoplot.bench_mark() provides a more informative error if the ggbeeswarm package is not installed (@coatless, #69).

• Update documentation of bench_mark columns (@jdblischak, #67).