Fixed channel parsing.

Sometimes the channel is included in the frequency return, but other
times it is not, so now the regex for parsing the channel is more
flexible to allow for that eventuality.  Thanks to @gavinwahl (#33) and
@qizha (#39) for raising the issue.

Conflicts:
	tests/test_parsing.py

(cherry picked from commit 08c648ad97627ba7f8314557cbb3d553c0854d1d)
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.

(cherry picked from commit fe79e799f2d3862e4764c69e76ed5a7d0a132002)
some wifi have quality as 'Quality:38  Signal level:0  Noise level:0'

(cherry picked from commit 0173f3712bc350335316f99e9ee2fa6e766e7424)
Moved CHANGES.rst to root of project

(cherry picked from commit e90944c592a76a63293525054c8d80c97ad27892)
Changes for 0.3.3

(cherry picked from commit 9546fc9aacb6d8c6c5674a7f9db886f598f164d0)
Version 0.3.3