Update .travis.yml

Build code in debug configuration...
Bugfix: allow compilation with __DEBUG__.

The argument idx_ is only used in an ASSERT; ASSERT, in turn, is a
no-op unless __DEBUG__ is defined.  So, when __DEBUG__ is not defined,
gcc would warn about an unused variable if the name is declared.

Allow debug and warning-free non-debug compilation to occur by making
argument name declaration conditional on __DEBUG__.
Bugfix: change isAccessedTransposed() to doAccessTransposed.

This is a best-guess fix to allow compilation when __DEBUG__ is defined.
Buildfix: Define __DEBUG__ for CMAKE_BUILD_TYPE Debug.

This seems like the likely intent of the conditional compilation
on__DEBUG__ in acado_debugging.hpp, etc.

It might be better to take a leaf out of <assert.h>, and use NDEBUG
instead.
WarningFix: remove always-true expression in assertion.

The variable being checked for non-negativity is an unsigned int.
Bugfix: acadoIsEqual should use fabs() for rel vs abs decision.

Code previously used maximum of signed arguments to decide whether to
use relative or absolute tolerance check.  If this function is to also
be used to compare negative numbers of large magnitude, the absolute
value of its arguments should be used.
Minor: whitespace fix.
Update CompilerOptions.cmake

Trying to remove unused-comparison with clang...
Removed old makefile and the mainpage -- doxygen related
Updated debugging tools section
Added markdown wiki to the repo -- the same, a bit updated, content from the SF website
Updated main doxygen file to compile the new markdown pages
Merge branch 'master' of https://github.com/mvukov/acado
Removed a few varnings that Clang was constantly reporting...
Merge branch 'debug-fixes' of github.com:roryyorke/acado into roryyorke-debug-fixes
Merge branch 'isequal-uses-fabs-2' of github.com:roryyorke/acado into roryyorke-isequal-uses-fabs-2
Removed some warnings
Merge branch 'master' of github.com:acado/acado
small bug fix related to automatic MEX build script and Simulink exported interface