Update .travis.yml

Last: #516
Changing into root of project before calling make.

This is just a change to the travis config for the travis build.
Allowing travis-ci to update submodules.
Adding cd into NUPIC before running tests.
Updated README for CMake
Removing submodule work within build.sh
Merge branch 'master' of github.com:numenta/nupic into david-patch-2
Trying to set default cpp compiler to GSS
Reverting change to default cpp compiler (didn't work).
Trying David's suggestion about default compiler
Reverting previous CMake default compiler fix.

Because it didn't work. Trial and error with Travis at this point.
Added -Wsign-compare compile option for gcc.

In an attempt to make travis gcc matrix happy.
Removing -std=c++0x compile option for gcc.

This option seemed to be affecting gcc builds. Trying its removal to see if it helps with CI.
Fixed -Wno-sign-compare warning option.

As suggested by @DavidRagazzi.
Merge branch 'master' into david-patch-2
Merge branch 'david-patch-2' of github.com:rhyolight/nupic into david-patch-2
Update CMakeLists.txt
Update CMakeLists.txt
Update CMakeLists.txt
Update CMakeLists.txt