Support features on the command line

[agubler]

Adds support for passing features via the command line and overrides the flags that are configured in the .dojorc.

# sets foo to true
dojo build -f foo

# sets foo to foo
dojo build -f foo=foo

# sets foo to foo and bar to true
dojo build -f foo=foo -f bar

Resolves #103

[codecov]

Codecov Report

Merging #149 into master will decrease coverage by 0.89%.
The diff coverage is 40%.

@@           Coverage Diff           @@
##           master   #149     +/-   ##
=======================================
- Coverage   56.89%    56%   -0.9%     
=======================================
  Files           8      8             
  Lines         464    475     +11     
  Branches      112    113      +1     
=======================================
+ Hits          264    266      +2     
- Misses        200    209      +9

Impacted Files	Coverage Δ
src/main.ts	93.12% <40%> (-6.88%)	⬇️

---

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 3213b6b...8143a18. Read the comment docs.