Merge pull request #264 from arxanas/style-guide

Added style guide.

CONTRIBUTING.md

+# Style Guide #
+
+### Compatibility ###
+
+Cockatrice is written in C++-03, so do not use C++11 constructs such as `auto`.
+
+Cockatrice support both Qt 4 and Qt 5, so make sure that your code compiles
+with both. If there have been breaking changes between Qt 4 and 5, use a
+statement such as
+
+    #if QT_VERSION >= 0x500000
+        doSomethingWithQt5();
+    #else
+        doSomethingWithQt4();
+    #endif
+
+For consistency, use Qt data structures where possible, such as `QString` over
+`std::string` or `QList` over `std::vector`.
+
+### Header files ###
+
+Use header files with the extension `.h` and source files with the extension
+`.cpp`.
+
+Use header guards in the form of `FILE_NAME_H`.
+
+Simple functions, such as getters, may be written inline in the header file,
+but other functions should be written in the source file.
+
+Keep library includes and project includes grouped together. So this is okay:
+
+    // Good:
+    #include <QList>
+    #include <QString>
+    #include "card.h"
+    #include "deck.h"
+
+    // Good:
+    #include "card.h"
+    #include "deck.h"
+    #include <QList>
+    #include <QString>
+
+    // Bad:
+    #include <QList>
+    #include "card.h"
+    #include <QString>
+    #include "deck.h"
+
+### Naming ###
+
+Use `UpperCamelCase` for classes, structs, enums, etc. and `lowerCamelCase` for
+function and variable names.
+
+Member variables aren't decorated in any way. Don't prefix or suffix with
+underscores, etc.
+
+For arguments to constructors which have the same names as member variables,
+prefix those arguments with underscores:
+
+    MyClass::MyClass(int _myData)
+        : myData(_myData)
+    {}
+
+Pointers and references should be denoted with the `*` or `&` going with the
+variable name:
+
+    // Good:
+    Foo *foo1 = new Foo;
+    Foo &foo2 = *foo1;
+
+    // Bad:
+    Bar* bar1 = new Bar;
+    Bar& bar2 = *bar1;
+
+Use `0` instead of `NULL` (or `nullptr`) for null pointers.
+
+### Braces ###
+
+Use K&R-style braces. Braces for function implementations go on their own
+lines, but they go on the same line everywhere else:
+
+    int main()
+    {
+        if (someCondition) {
+            doSomething();
+        } else {
+            while (someOtherCondition) {
+                doSomethingElse();
+            }
+        }
+    }
+
+Braces can be omitted for single-statement if's and the like, as long as it is
+still legible.
+
+### Tabs ###
+
+Use only spaces. Four spaces per tab.
+
+### Lines ###
+
+Do not have trailing whitespace in your lines.
+
+Lines should be 80 characters or less, as a soft limit.