consistent example names

[ranocha]

Closes #244. I cancelled the Travis CI build since we don't need it here.

[codecov]

Codecov Report

Merging #320 (7f11db8) into dev (406ccc2) will decrease coverage by 1.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##              dev     #320      +/-   ##
==========================================
- Coverage   89.38%   88.34%   -1.05%     
==========================================
  Files          84       84              
  Lines       13381    13381              
==========================================
- Hits        11961    11821     -140     
- Misses       1420     1560     +140     

Flag	Coverage Δ
unittests	88.34% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/semidiscretization_euler_gravity.jl	78.83% <ø> (ø)
src/timedisc/timedisc.jl	82.11% <ø> (ø)
src/timedisc/timedisc_euler_gravity.jl	61.68% <ø> (-28.98%)	⬇️
src/run_euler_gravity.jl	81.65% <0.00%> (-11.84%)	⬇️
src/amr/amr.jl	86.00% <0.00%> (-8.00%)	⬇️
src/solvers/dg/2d/amr.jl	88.46% <0.00%> (-7.70%)	⬇️
src/equations/2d/compressible_euler.jl	84.50% <0.00%> (-7.40%)	⬇️
src/equations/2d/hyperbolic_diffusion.jl	82.72% <0.00%> (-3.67%)	⬇️
src/solvers/dg/2d/dg.jl	91.89% <0.00%> (-1.17%)	⬇️

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[sloede]

With one typo fixed, this can be merged.