fix a typo : 'proress' instead of 'progress'
Merge pull request #29 from remyzorg/master

fix a typo : 'proress' instead of 'progress'
Replace fake boolean by actual booleans.
Make camlp4 an optionnal dependency.
Merge pull request #30 from ocsigen/bool_attrib

Replace fake boolean by actual booleans.
Merge pull request #32 from ocsigen/opt-camlp4

Make camlp4 an optionnal dependency.
Formatting.

Closes #25