CLN/PERF: Do not import matplotlib at the module level.
Merge pull request #112 from danielballan/no-mpl-import

CLN/PERF: Do not import matplotlib at the module level.
CLN: On first run of FFTW, print info statement instead of ugly warning. Also fix typo.
Merge pull request #115 from danielballan/fftw-message

CLN: Change info on first run of FFTW.
FIX: Fix typo introducing in #112 mpl cleanup.
Merge pull request #117 from danielballan/fix-mpl-typo

FIX: Fix typo introducing in #112 mpl cleanup.