doctests failing

[compenguy]

@LucaCappelletti94 with the merge of PR #10 , we have numerous test failures:

failures:
    src/corpus_par_from.rs - corpus_par_from::Corpus<KS,NG,K,WeightedBitFieldBipartiteGraph>::par_from (line 111)
    src/lib.rs - (line 103)
    src/lib.rs - (line 158)
    src/lib.rs - (line 187)
    src/lib.rs - (line 217)
    src/lib.rs - (line 246)
    src/lib.rs - (line 280)
    src/lib.rs - (line 301)
    src/lib.rs - (line 343)
    src/lib.rs - (line 375)
    src/lib.rs - (line 471)
    src/lib.rs - (line 580)
    src/lib.rs - (line 79)

test result: FAILED. 119 passed; 13 failed; 0 ignored; 0 measured; 0 filtered out; finished in 11.39s

They all seem to be doctest failures, I think