Fix a bug in pclearbot

Fix a bug in pcofix with handling hypotheses with existential quantif…

…iers.

Fix a bug in pclearbot using pclearbotH

Bug fix: pcofix renamed variable names 'x0,x1' into 'x2,x3'

Update README.md

Fix pcofix bug #41

Remove unused imports and tactics

Fix the following bug.

#34 (comment)

Merge pull request #38 from minkiminki/grespectful

More general respectful functor

Exclude example_upto.v from installation