Fixes #50: Use standard chef/knife formatting for all knife decrypt output
Went through files and removed use of brackets where command-line
arguments are mandatory.  Left brackets in where arguments are
optional.

Minor formatting - whitespace removal, fixed an indent on a def.

Updated README.md and KNIFE_EXAMPLES.md to include formatting options.
Merge pull request #64 from eklein/issue-50

Issue 50: Use standard chef/knife formatting for all knife decrypt output