boost: Use wildcard in version for bbappend

Makes it apply to any version of boost from here on.

Signed-off-by: Khem Raj <raj.khem@gmail.com>
README: Add bitbake > 1.20 dependency

Document the specific versions of bitbake needed
Add myself to contributor list

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Merge pull request #218 from kraj/master

boost: making bbappend version-independent