feat: adds an 'isFunction' function

[mitchellporter]

closes #100

[codecov-io]

Codecov Report

Merging #102 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master   #102   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files          35     36    +1     
  Lines         103    105    +2     
=====================================
+ Hits          103    105    +2

Impacted Files	Coverage Δ
src/is-function.js	100% <100%> (ø)

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[kentcdodds]

Looks awesome! Just one thing, could you do me a favor and remove the package-lock.json and add an entry for it in the .gitignore? I want to avoid people having to deal with merge conflicts in that file. Let me know if you need my help. Thank you so much!

[mitchellporter]

Sure thing! I've removed package-lock.json and added it to the .gitignore as well.

Would you like me to squash the commits?

[kentcdodds]

Excellent! Thanks so much! Don't worry about the commits, I can squash then and even with a new commit message via the GitHub UI (one of my favorite new features!)

[mitchellporter]

Awesome thanks again for putting this all together cheers!