Changebonds refactor

[lkdvos]

• changebonds now always returns normalized states
• docstrings
• refactor duplicate code Fixes #70

[codecov[bot]]

Codecov Report

Merging #81 (ca70e2a) into master (21ad2c0) will decrease coverage by 0.12%. Report is 1 commits behind head on master. The diff coverage is 93.04%.

@@            Coverage Diff             @@
##           master      #81      +/-   ##
==========================================
- Coverage   84.37%   84.26%   -0.12%     
==========================================
  Files          60       61       +1     
  Lines        3745     3711      -34     
==========================================
- Hits         3160     3127      -33     
+ Misses        585      584       -1     

Files	Coverage Δ
src/MPSKit.jl	100.00% <ø> (ø)
src/algorithms/changebonds/changebonds.jl	100.00% <100.00%> (ø)
src/algorithms/changebonds/optimalexpand.jl	100.00% <100.00%> (ø)
src/algorithms/changebonds/randexpand.jl	100.00% <100.00%> (ø)
src/states/mpsmultiline.jl	81.08% <0.00%> (-2.26%)	:arrow_down:
src/algorithms/changebonds/vumpssvd.jl	71.05% <0.00%> (+3.55%)	:arrow_up:
src/algorithms/changebonds/svdcut.jl	85.71% <83.33%> (+1.09%)	:arrow_up:

... and 1 file with indirect coverage changes