Compilation fixes

readme.md: improve build status rendering by Doxygen

unittest.h: make sure to #include <stdexcept>

See https://github.com/miloyip/rapidjson/commit/a2a0d161#commitcomment-9838110

Doxygen currently does not support images with links, which breaks the
current rendering of the front page at https://miloyip.github.io/rapidjson.

Move the status badges to a table with the links in the top-row instead.

While at it, add a description below the logo and put the GitHub and
documentation links into in itemisation.

error.h: drop trailing comma in enum

In C++'98/03, trailing commas in enumerations are not allowed, but have
been introduced in C++11. This patch drops the trailing commas in order
to avoid compiler warnings (e.g. GCC with -pedantic).

See #9 and http://code.google.com/p/rapidjson/issues/detail?id=49 for
previous instances of this issue.

add AppVeyor CI support for checked Windows builds

Move `gtest_force_shared_crt` option to Win32 VC only.

Mentioned in #240

Fix typesetting

CMake support

reader.h: warning fixes (closes #235, closes #236)

Reorganized some features. Try to make the text clearer in features and
tutorial.

Add std::string overload to Writer when RAPIDJSON_HAS_STDSTRING defined

Use aligned SSE register load intrinsic.

The code goes to the trouble of ensuring that data is aligned at a
16-byte boundary, then goes ahead and uses the unaligned form of the
load intrinsic _mm_loadu_si128.

Either the code shouldn't bother aligning the data to the start of the
whitespace, or it should use the aligned form of the intrinsic.

Correct Value(kStringType) and more assertions