Update .gitignore
Update README.md -- OSX support, Ninja build
Add forall, foldl, foldr to sexpr_funcs
Add more tests on sexpr_funcs
Update format.cpp & format.h + Update format tests
Update .travis.yml to send an email to the mailing list (leansmt-dev@googlegroups.com)
Use 'nullptr' instead of '0'
Update format
1) operator+ is <> (previously, it was a + b = a <> ' ' <> b)
2) using sstream to compute length of text
Add pp to expr
Update README.md
Update .travis.yml to send build logs only to leansmt-dev list.
Fix performance bug in format, add paren combinator
Update format.cpp, flatten(LINE) = "" instead of " "
Add more to expr pretty-print
Update .travis.yml to fix email a notification setting.
 - It seems that googlegroups doesn't accept emails from travis-ci
 directly. I set up an email-forwarding on my account to pass emails
 from travis to the mailing list.
Rename normalize context to local_context. Create context. Fix bug in name.cpp

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Add type checker. Fix normalization with non-empty context

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Normalize level expressions

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Fix bugs in type checker

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>