update version number after adding some features

features added:
  - Pass user-specified variables to the async process
  - Make a couple variables `defcustom'

update version number to 0.5.1

update a major version number after a major refactor by seven monier

Update org-auto-tangle.el

Update version number to release the added patches

make the version option meets the release tag

Merge pull request #17 from RampedIndent/patch-1

Added Safe-list usage to readme

Merge pull request #13 from fredericgiquel/babel-evaluation

Permit code block evaluation for files in safelist

Merge pull request #13 from fredericgiquel/babel-evaluation

Permit code block evaluation for files in safelist

Update org-auto-tangle.el

Merge pull request #7 from zzamboni/master

Improve auto_tangle regex