Update free-programming-books-gr.md
Added "Agile Android Software Development" eBook

Added "Agile Android Software Development" eBook in the list under the Android section.  The book is currently in writing progress, but new chapters are released as soon they are copy-edited.  "Release 1.0" is expected in January 2015.
Merge pull request #1136 from Symbiosoft/master

Added "Agile Android Software Development" eBook
added to index as requested
Merge pull request #1138 from borgified/patch-2

Patch 2