Allow Diactoros 1.3 or 2.0

[Firehed]

Will allow consumers of the API framework to use either version

[codecov]

Codecov Report

Merging #88 into 3_2_0 will increase coverage by 0.01%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##              3_2_0      #88      +/-   ##
============================================
+ Coverage     96.05%   96.06%   +0.01%     
  Complexity      119      119              
============================================
  Files            26       26              
  Lines           355      356       +1     
============================================
+ Hits            341      342       +1     
  Misses           14       14

Impacted Files	Coverage Δ	Complexity Δ
src/Dispatcher.php	98.48% <100%> (+0.01%)	45 <0> (ø)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update a502c13...492cb9e. Read the comment docs.