Tries a new travis configuration

[flovilmart]

Reduces build times from 5-7 minutes to 3-4 minutes.

These images are bigger (e.g. 7.5 GB RAM vs 4 GB shared RAM) and aren't sharing the CPU and RAM like on our container-based infrastructure where your builds are currently running. The boot time is slightly higher (20-60s instead of 1-6s)

[codecov-io]

Current coverage is 92.37% (diff: 100%)

Merging #2645 into master will increase coverage by 0.29%

@@             master      #2645   diff @@
==========================================
  Files            99        100     +1   
  Lines         12113      12798   +685   
  Methods        1488       1722   +234   
  Messages          0          0          
  Branches       1996       2388   +392   
==========================================
+ Hits          11154      11822   +668   
- Misses          959        976    +17   
  Partials          0          0          

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