Precompilation is pretty slow

[tlnagy]

It takes a minute to load Gadfly the first time, for example:

time julia -e 'using Gadfly'
INFO: Recompiling stale cache file /Users/tamasnagy/.julia/lib/v0.4/Gadfly.ji for module Gadfly.
julia -e 'using Gadfly'  57.55s user 0.68s system 100% cpu 57.972 total

version

Julia Version 0.4.5
Commit 2ac304d* (2016-03-18 00:58 UTC)
Platform Info:
  System: Darwin (x86_64-apple-darwin15.4.0)
  CPU: Intel(R) Core(TM) i7-4850HQ CPU @ 2.30GHz
  WORD_SIZE: 64
  BLAS: libopenblas (DYNAMIC_ARCH NO_AFFINITY Haswell)
  LAPACK: libopenblas
  LIBM: libopenlibm
  LLVM: libLLVM-3.3

Definitely doesn't present the best view of julia to new users.

[tlnagy]

Might be related to #15048

[yuyichao]

Close as dup. Gadfly does have a lot of dependencies.