Bump DataFrames to 1

[tmigot]

The constructor DataFrame(types, names, 0) is has been removed from DataFrames.jl. So, I used the one suggested in this discussion after DataFrames' modification.

I dropped DataFrames 0.22 as it has no compatible environment here, but surprisingly 0.21 does.

I expect the unit test to pass on the nightly at this point.

[codecov]

Codecov Report

Merging #91 (03f240d) into master (81a90b6) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master      #91   +/-   ##
=======================================
  Coverage   76.30%   76.30%           
=======================================
  Files          13       13           
  Lines         287      287           
=======================================
  Hits          219      219           
  Misses         68       68           

Impacted Files	Coverage Δ
src/pkgbmark.jl	76.31% <100.00%> (ø)
src/run_solver.jl	86.11% <100.00%> (ø)

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[tmigot]

So, it doesn't pass the nightly tests with a new error that has been added yesterday as an issue in JLD2.jl.

[dpo]

Let's move on.