add feature list to readme

[oxinabox]

to merge after #10
though for good PERT charts need #8

[codecov-io]

Codecov Report

Merging #11 into master will increase coverage by 0.71%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #11      +/-   ##
==========================================
+ Coverage   91.78%   92.50%   +0.71%     
==========================================
  Files           5        5              
  Lines          73       80       +7     
==========================================
+ Hits           67       74       +7     
  Misses          6        6              

Impacted Files	Coverage Δ
src/graph_viz.jl	97.14% <0.00%> (+0.36%)	⬆️
src/timing_graphs.jl	89.47% <0.00%> (+0.58%)	⬆️
src/timing_distributions.jl	87.50% <0.00%> (+1.13%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 2aa9749...14a7d2c. Read the comment docs.