Addons

  * CONDA_ADDON: overwrite_build_num, overwrite_build_string 
                 in .condar config file
  * CONDA_ADDON: class MetaData: added: def build_string
  * CONDA_ADDON: option in .condar config file for many build flags
  * CONDA_ADDON: https://github.com/pydata/conda in INSTALL.rst  issue: #418 
  * CONDA_ADDON: for build: user option to install the package within
                 the build process