rush v0.6.0

• rush v0.6.0
  • fix variables containing "{}", the bug was introduced in v0.5.7. e.g., rush -v 'p={}/{%}' 'echo {p}_1.fq' outputs a/b/b_1.fq.
  • supports outputting "{}" with the replacement string "{{}}". echo a/b | rush 'echo {{}}' outputs {}.