Fix SpaceBeforeFirstArg cop for multiline argument

and exclude assignments
Merge pull request #945 from cschramm/space_before_first_arg

Fix SpaceBeforeFirstArg cop for multiline arguments
[Fix #948] Avoid auto-correction changing code meaning in Blocks

Re-parse and check that the AST hasn't changed when doing auto-
correct in Blocks cop.
[Refactor] Extract module AutocorrectUnlessChangingAST
Merge pull request #959 from jonas054/fix_948_do_end_auto_correct

Fix do end auto-correct
[Fixed #946] Allow non-nil checks that are the final expression of a
predicate method definition
[Fix #957] Allow space + comment inside ( { and [
Merge pull request #960 from jonas054/fix_957_space_inside

[Fix #957] Allow space + comment inside ( { and [
Bump version to 0.20.1