More crate updates

[str4d]

Includes a fix for a bellman compile bug introduced in #104.

[codecov-io]

Codecov Report

Merging #127 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master    #127   +/-   ##
======================================
  Coverage    56.2%   56.2%           
======================================
  Files          43      43           
  Lines        6120    6120           
======================================
  Hits         3440    3440           
  Misses       2680    2680

Impacted Files	Coverage Δ
bellman/src/gadgets/test/mod.rs	66.5% <100%> (ø)	⬆️

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[ebfull]

It'd be nice to see if we can rely on just one of these subcrates of crossbeam rather than crossbeam and all of these other crates. (Not blocking.)

[daira]

utACK