Add docs about how to update notmuch-abook in post-new hook
Make code snippet more general

ie remove options and paths particular to my set up
Add note about snippet being shell syntax
Syntax error in markdown
Add --abook-output option to lookup

This is email\tname - so it is easy to unambiguously parse the output,
and if there is no name it is still easy to parse.
Merge pull request #1 from foobacca/doc-notmuch-new

merge more doc in README
Merge pull request #2 from foobacca/abook-format

Add --abook-output option to lookup