Merge branch 'improve_readme' into 'master'

Improve README.md

See merge request !89
5 jobs for master in 14 minutes and 25 seconds (queued for 8 minutes and 27 seconds)
Status Job ID Name Coverage
  Test
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test_min

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test_mpi

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test_mpi_fftw

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test_mpi_fftw_hdf5

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  Release
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release_image_master

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