feat: create classes RandText, RandTextSrc and RandTextLen

[rafamizes]

Closes #29

[codecov]

Codecov Report

Merging #30 (4729b9c) into master (bb35e25) will increase coverage by 0.21%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #30      +/-   ##
==========================================
+ Coverage   93.14%   93.36%   +0.21%     
==========================================
  Files          62       63       +1     
  Lines         905      934      +29     
==========================================
+ Hits          843      872      +29     
  Misses         62       62              

Impacted Files	Coverage Δ
lib/src/rand/rand.dart	100.00% <ø> (ø)
lib/src/rand/rand_dig.dart	100.00% <ø> (ø)
lib/src/rand/rand_hex.dart	100.00% <ø> (ø)
lib/src/rand/rand_text.dart	100.00% <100.00%> (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 bb35e25...4729b9c. Read the comment docs.

[rafamizes]

@rultor merge it.

[rultor]

@rultor merge it.

@rafamizes OK, I'll try to merge now. You can check the progress of the merge here

[rultor]

@rultor merge it.

@rafamizes Done! FYI, the full log is here (took me 2min)