Only support latest stable Laravel version

[dmason30]

Follows laravel-shift/blueprint#496 in dropping support for legacy laravel versions in a new major version.

Support for older versions of Laravel has created a drag on this package. To make maintenance and contributions easier, Blueprint will only support the latest stable Laravel versions.

To make a clean break, this change will be reflected by a major version number increase (2.0). However, future major versions will on increase to reflect changes to Blueprint's grammar, not simply new Laravel versions.

[codecov]

Codecov Report

Merging #28 (804bb34) into master (e2a924e) will increase coverage by 0.28%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master      #28      +/-   ##
============================================
+ Coverage     94.83%   95.12%   +0.28%     
+ Complexity      160      155       -5     
============================================
  Files            27       26       -1     
  Lines           523      513      -10     
============================================
- Hits            496      488       -8     
+ Misses           27       25       -2     

Impacted Files	Coverage Δ
src/Builders/Concerns/BuildsFactoryStatements.php	100.00% <ø> (ø)
src/Builders/Statements/StatementBuilder.php	100.00% <ø> (+20.00%)	⬆️
src/Actions/MakeHttpTests.php	100.00% <100.00%> (ø)
src/Builders/HttpTestBuilder.php	100.00% <100.00%> (ø)
src/Builders/PendingOutput.php	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 e2a924e...804bb34. Read the comment docs.