Add license headers

[odow]

x-ref jump-dev/MathOptInterface.jl#1813

[codecov]

Codecov Report

Merging #314 (62ec661) into master (2016f03) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #314   +/-   ##
=======================================
  Coverage   87.71%   87.71%           
=======================================
  Files           3        3           
  Lines         692      692           
=======================================
  Hits          607      607           
  Misses         85       85           

Impacted Files	Coverage Δ
src/C_wrapper.jl	86.95% <ø> (ø)
src/Ipopt.jl	100.00% <ø> (ø)
src/MOI_wrapper.jl	87.80% <ø> (ø)

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