rspec let to stop repetation of same code

using let of rspec for non repetative declaration
Merge pull request #947 from rajcybage/fix_spec

rspec `let` to stop repetation of same code
Revert "rspec let to stop repetation of same code"

This reverts commit f6318f6e60b7cc317c65658063db5fbeb5130848.

We should test both `:str_field` and `:strField`.
Fixed javadoc for getRubyCasedName
Use normal "new" logic in Regexp. Fixes #955.
Set `jruby.jit.exclude` method to `''`.

The old default `none` prevents a method named `none` to be
JIT-compiled.

Fixes #954.
Remove mention of .jrubyrc for C Extensi building [skip ci]

Fixes #953
Enabling C Extensions via `.jrubyrc` is not effective for building gems,
so remove the mention of it to avoid confusion.
Change `--properties` output for null default opts [skip ci]

Fixes #949

For options whose default is `null`, it is confusing to print out the
string `null`, since it is not a likely value that the user can use.
While the message makes it clear that the value will be interpreted as a
String, it is a good idea to leave it blank instead, so that the user
can fill it themselves.