Fix violations of PEP 8(Style Guide).

This commit fixes various violations of PEP 8. Most of the changes are shortening of lines longer than 79 characters. Compatibility to PEP 8 was checked using Flake-8 and the vim plugin (vim-flake8). Violations because of 'modules being imported and not used'  were left as it is. These are mostly 'unfixable'.