get rid of Compat requirement

[bjarthur]

fixes #11

[coveralls]

Coverage decreased (-93.3%) to 6.742% when pulling e878199 on bjarthur:bja/compat into e293b7b on JuliaNLSolvers:master.

[codecov]

Codecov Report

Merging #12 into master will decrease coverage by 92.22%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #12       +/-   ##
==========================================
- Coverage     100%   7.77%   -92.23%     
==========================================
  Files           2       3        +1     
  Lines           6      90       +84     
==========================================
+ Hits            6       7        +1     
- Misses          0      83       +83

Impacted Files	Coverage Δ
src/types.jl	3.84% <ø> (-96.16%)	⬇️
src/OptimBase.jl	100% <ø> (ø)
src/api.jl	7.93% <0%> (-92.07%)	⬇️

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[bjarthur]

this is ready i think. comments?

[martinholters]

I'm also a bit hampered by #11 and would appreciate it if this could merged and a new release tagged soonish.

[Vaibhavdixit02]

Bump @pkofod

[ChrisRackauckas]

and add CompatHelper please.