Pretty print let expressions

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

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Fix bug in parser.

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

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Run examples during testing

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Add support for reading input files from the command line.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Add parse_level. Fix bug at environment::is_ge

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Fix bug in level.cpp. Add new example

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Fix cup symbol. In Emacs, the unicode characters cup and cap are assigned incorrectly.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Update .travis.osx.yml to copy precompiled binaries to dropbox