`session_id` instead of `session_name` in copycat file

This plugin had issues fetching copycat files if those files were having
'spaces' in them. spaces could happen if copycat session name also
contained a space.

This commit fixes that by switching to using `session_id` instead of
session name.

Fixes #32
Add credits for the last commit
Use grep -E and remove eval
Remove backslashes in default patterns
Remove backslashes in copycat_git_special.sh
Update tests
Update changelog and the readme for grep -E feature
Fix custom search tests (remove backslash)
v2.0.0
Update readme