Rewrite README in Markdown (#277)

* Use *sections* to make the README more structured and easier to read.
* Use *code blocks* for scripts.
* Use *links* for the homepage and for the LICENSE file.

README.md

+# dlib C++ library
+
+Dlib is a modern C++ toolkit containing machine learning algorithms and tools for creating complex software in C++ to solve real world problems. See [http://dlib.net](http://dlib.net) for the main project documentation and API reference.
+
+
+
+## Compiling dlib C++ example programs
+
+Go into the examples folder and type:
+
+```bash
+mkdir build; cd build; cmake .. ; cmake --build .
+```
+   
+That will build all the examples.  
+If you have a CPU that supports AVX instructions then turn them on like this:
+    
+```bash
+mkdir build; cd build; cmake .. -DUSE_AVX_INSTRUCTIONS=1; cmake --build .
+```
+
+Doing so will make some things run faster.
+
+
+
+## Compiling dlib Python API
+
+Before you can run the Python example programs you must compile dlib. Type: 
+
+```bash
+python setup.py install
+```
+
+or type
+
+```bash
+python setup.py install --yes USE_AVX_INSTRUCTIONS
+```
+   
+if you have a CPU that supports AVX instructions, since this makes some things run faster.  
+
+
+
+## Running the unit test suite
+
+Type the following to compile and run the dlib unit test suite:
+
+```bash
+cd dlib/test
+mkdir build
+cd build
+cmake ..
+cmake --build . --config Release
+./dtest --runall
+```
+
+Note that on windows your compiler might put the test executable in a subfolder called `Release`. If that's the case then you have to go to that folder before running the test.
+
+This library is licensed under the Boost Software License, which can be found in [dlib/LICENSE.txt](https://github.com/davisking/dlib/blob/master/dlib/LICENSE.txt).  The long and short of the license is that you can use dlib however you like, even in closed source commercial software.
+
+## dlib sponsors
+
+This research is based in part upon work supported by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA) under contract number 2014-14071600010. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of ODNI, IARPA, or the U.S. Government.  
+

README.txt

-
-                              dlib C++ library
-
-Dlib is a modern C++ toolkit containing machine learning algorithms and tools
-for creating complex software in C++ to solve real world problems.  See
-http://dlib.net for the main project documentation and API reference.
-
-
-
-COMPILING DLIB C++ EXAMPLE PROGRAMS
-   Go into the examples folder and type:
-       mkdir build; cd build; cmake .. ; cmake --build .
-   That will build all the examples.  If you have a CPU that supports AVX
-   instructions then turn them on like this:
-       mkdir build; cd build; cmake .. -DUSE_AVX_INSTRUCTIONS=1; cmake --build .
-   Doing so will make some things run faster.
-
-COMPILING DLIB Python API
-   Before you can run the Python example programs you must compile dlib. Type:
-       python setup.py install
-   or type
-       python setup.py install --yes USE_AVX_INSTRUCTIONS
-   if you have a CPU that supports AVX instructions, since this makes some
-   things run faster.  
-
-RUNNING THE UNIT TEST SUITE
-   Type the following to compile and run the dlib unit test suite:
-       cd dlib/test
-       mkdir build
-       cd build
-       cmake ..
-       cmake --build . --config Release
-       ./dtest --runall
-
-   Note that on windows your compiler might put the test executable in a
-   subfolder called Release.  If that's the case then you have to go to that
-   folder before running the test.
-
-This library is licensed under the Boost Software License, which can be found
-in dlib/LICENSE.txt.  The long and short of the license is that you can use
-dlib however you like, even in closed source commercial software.
-
-Dlib Sponsors:
-  This research is based in part upon work supported by the Office of the
-  Director of National Intelligence (ODNI), Intelligence Advanced Research
-  Projects Activity (IARPA) under contract number 2014-14071600010. The
-  views and conclusions contained herein are those of the authors and
-  should not be interpreted as necessarily representing the official policies
-  or endorsements, either expressed or implied, of ODNI, IARPA, or the U.S.
-  Government.  
-