Check for write access for bashcompletion via os.access

Alternative version of pull request rockymeza/wifi#41 (which apparently
isn't worked on any more) which checks for write access before
attempting to install the bashcompletion addition during
installation -- if only installed in a library into a virtualenv
the installation will now complete without an issue.
some wifi have quality as 'Quality:38  Signal level:0  Noise level:0'
Moved CHANGES.rst to root of project
Changes for 0.3.3
Don't forget to include CHANGES.rst.
Changes for 0.3.4