update linux travis build (#224)

* update linux travis build

- Note: this is using `cmake 3.2.2`, not `2.8.12`.
- It seems you can alternatively install `cmake` from source
- No trusted `2.8.12` PPA are available on travis at this time.
- Added some (missing?) linux gfx build deps.

* add osx cmake version for test clarity

.travis.yml

@@ -1,4 +1,5 @@
 language: cpp
+dist: trusty
 sudo: false
 matrix:
   include:
@@ -16,18 +17,21 @@ matrix:
             - python3.5-dev
             - python3.5-venv
             - libglu1-mesa-dev
-            - libxxf86vm-dev 
+            - libxxf86vm-dev
             - libxrandr-dev
             - libxinerama-dev
             - libxcursor-dev
             - libxi-dev
+            - libx11-dev
             - cmake
       script:
+        - cmake --version
         - cmake -DNANOGUI_USE_GLAD=ON -DNANOGUI_PYTHON_VERSION=3.5 -DPYTHON_INCLUDE_DIRS:PATH=/usr/include/python3.5m -DPYTHON_LIBRARY:FILEPATH=/usr/lib/x86_64-linux-gnu/libpython3.5m.so -DCMAKE_CXX_COMPILER=g++-4.8 -DCMAKE_C_COMPILER=gcc-4.8
         - make -j 2
     - os: osx
       compiler: clang
       script:
+        - cmake --version
         - cmake -DNANOGUI_PYTHON_VERSION=2.7
         - make -j 2
     - os: linux

src/widget.cpp

@@ -200,7 +200,7 @@ Screen *Widget::screen() {
     }
 }
 
-void Widget::requestFocus() {
+void Widget::request_focus() {
     Widget *widget = this;
     while (widget->parent())
         widget = widget->parent();