Cache Elm Dependencies to Speed-up Build on Circle-CI

[Nelson]

At present one of our projects takes 8 minutes to download and compile the Elm App:

Todo

• Figure out how to cache elm dependencies on CircleCI (we will do Travis-CI second)
• Apply to CI Client Project.
• Write-up steps with sample code in learn-elm and link to from learn-circleci

Priority-1 because this wastes time every CI build which slows down our dev workflow... ⏳ 💸 🔥
@SimonLab if you have time to help investigate this please go for it! (otherwise I will look at it soon...)

[Nelson]

This is a log of recent builds the average is 9 minutes:

Notice how the Top (most recent) build is "NOT RUNNING" because this project only has one "container" on CircleCI so it has to wait in a Queue until the current running build completes.

We could "just throw money at the problem" (by increasing the number of "containers" on CircleCI)
But that does not solve the problem of slow builds; all it would do is reduce the bottleneck, but we would still have a 9-10 minute wait for each each build. 😞

[Nelson]

One of our projects just took 44 minutes to run elm compile ... 😮 ⏳