Document the heap profile format.
Document the heap profile format.

This resolves #258.

cpeterso/jemalloc,jemalloc/jemalloc-cmake,jemalloc/jemalloc-cmake,leebaok/jemalloc-4.2.1-readcode,cpeterso/jemalloc,AndroidExternal/jemalloc,glandium/jemalloc,8l/jemalloc,AndroidExternal/jemalloc,cpeterso/jemalloc,glandium/jemalloc,wqfish/jemalloc,wqfish/jemalloc,wqfish/jemalloc,AndroidExternal/jemalloc,8l/jemalloc,AndroidExternal/jemalloc,wqfish/jemalloc,leebaok/jemalloc-4.2.1-readcode,wqfish/jemalloc,glandium/jemalloc,8l/jemalloc,leebaok/jemalloc-4.2.1-readcode,8l/jemalloc,jemalloc/jemalloc-cmake,jemalloc/jemalloc-cmake,cpeterso/jemalloc,leebaok/jemalloc-4.2.1-readcode,glandium/jemalloc