Remove Flag Generation

[asahasrabuddhe]

Update Travis YAML to remove generation command

Add support for Go 1.13
Drop support for Go 1.11

[asahasrabuddhe]

Looks like there is something wrong with the master as it is failing almost everything.

[codecov]

Codecov Report

Merging #881 into master will not change coverage.
The diff coverage is 69.04%.

@@           Coverage Diff           @@
##           master     #881   +/-   ##
=======================================
  Coverage   71.29%   71.29%           
=======================================
  Files          18       30   +12     
  Lines        2379     2379           
=======================================
  Hits         1696     1696           
  Misses        578      578           
  Partials      105      105

Impacted Files	Coverage Δ
flag.go	91.92% <ø> (+6.02%)	⬆️
docs.go	89.61% <ø> (ø)	⬆️
flag_generic.go	51.28% <51.28%> (ø)
flag_duration.go	55% <55%> (ø)
flag_uint.go	62.5% <62.5%> (ø)
flag_uint64.go	62.5% <62.5%> (ø)
flag_int64.go	65% <65%> (ø)
flag_string_slice.go	65.45% <65.45%> (ø)
flag_int64_slice.go	67.24% <67.24%> (ø)
flag_bool_t.go	70.45% <70.45%> (ø)
... and 18 more

---

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[asahasrabuddhe]

Current Status:

All essential checks are passing except the diff after generating TOC since I have removed the parts of code in README.md referencing ShortOptionHandling as they are not available for use in v1.21.0

[coilysiren]

All essential checks are passing except the diff after generating TOC since I have removed the parts of code in README.md referencing ShortOptionHandling as they are not available for use in v1.21.0

Can you put this inside another PR? We'll want to revert it after release 1.22.0 #867

[coilysiren]

Add support for Go 1.13
Drop support for Go 1.11

I would also like for this go inside it's own PR 🙏 unless there's some specific reason it's included in this one?