Added efficient bit rotate functions

[jakobnissen]

Changed the implementation of the xorshift_rotl methods. They now compile to something closer to a single bit rotate CPU instruction.

[codecov-io]

Codecov Report

Merging #61 into master will increase coverage by 0.21%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #61      +/-   ##
==========================================
+ Coverage   85.71%   85.93%   +0.21%     
==========================================
  Files          21       21              
  Lines         462      462              
==========================================
+ Hits          396      397       +1     
+ Misses         66       65       -1

Impacted Files	Coverage Δ
src/Xorshifts/common.jl	100% <100%> (ø)	⬆️
src/common.jl	100% <0%> (+11.11%)	⬆️

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[coveralls]

Coverage increased (+0.3%) to 84.257% when pulling 38b9ed6 on jakobnissen:master into 087acf3 on sunoru:master.

[coveralls]

Coverage increased (+0.3%) to 84.257% when pulling 38b9ed6 on jakobnissen:master into 087acf3 on sunoru:master.

[coveralls]

Coverage increased (+0.3%) to 84.257% when pulling 38b9ed6 on jakobnissen:master into 087acf3 on sunoru:master.

[sunoru]

Thanks a lot! I just checked it out and ran some benchmarks myself, and you are right.