Add snippet feature

[gdolle]

Add snippet code feature similarly to doxygen ability. See also the doxygen document guide for comment style.

Example:

We consider the following C++ code,

// test.cpp
#include <iostream>
/** [marker0] */
int main()
{
   //! [marker1]
   int a=0;
   //! [marker1]
   /// [marker2]
   int b=1;
   int c=2;
   /// [marker2]
   return 0;
}
/** [marker0] */

then both slice can be imported via

• [import:marker1](path/to/test.cpp)

   int a=0;

• [import:marker2](path/to/test.cpp)

   int b=1;
   int c=2;

• [include:marker0](path/to/test.cpp) (updated from @prudhomm comment)

int main()
{
   int a=0;
   int b=1;
   int c=2;
   return 0;
}

and does not depend on lines number in that case.

NB: C/C++, latex, python supported for now but could be improved.

[prudhomm]

very nice !

[azu]

@gdolle Thanks for nice feature!

Summary after I've reviewed.

• Split up marker feature to marker.js like language-detection.js.
  • (Of course, Slice feature also should be separated... After merging this pull request, I work on it)
• Need tests.

[prudhomm]

@gdolle @azu it would be nice to have an option to actually remove the // [marker1] lines from being included so that we have a nice clean code example.

consider a code that has all the markers, we go through all of them to explain the code (we don't show the markers). and then at the end we want to put the entire code. it would not be very nice to have all these // [marker] and there should be a flag to automatically remove them (enabled by default I would say).

[gdolle]

@azu @prudhomm I updated following the review comments, meaning:

• splitting the code in a separate file src/marker.js
• add several unit tests in test/marker-test.js
• fix const variable
• add hasMarker() function
• add removeMarker() function which remove inner markers following the suggestion of @prudhomm.

Note that I updated espower-babel which is deprecated now. (Test pass see travis. ;) )

[azu]

@gdolle Thanks for great work! I've merged it and publish 1.8.0.

[azu]

After merging, I found a breaking backward compatibily. I've opened pull request to fix that issue #13

[azu]

I've fixed regression issue #13 and publish 1.8.1.

Thanks again @gdolle @prudhomm