Update Emscripten SDK cleanly (#473)
Update Emscripten SDK cleanly (#473)

For some reason building with Emscripten changes some files in the
SDK which leads to errors when trying to update with "git pull":

    Updating 4eeff61..751355a
    error: Your local changes to the following files would be overwritten by merge:
            binaryen-tags.txt
            emscripten-tags.txt
            upstream/lkgr.json

    Please, commit your changes or stash them before you can merge.
    Aborting

Add a "git reset" before doing the pull to discard any local changes
and ensure a clean merge with the updated version.
cossacklabs/themis,cossacklabs/themis,cossacklabs/themis,cossacklabs/themis,cossacklabs/themis,cossacklabs/themis,cossacklabs/themis,cossacklabs/themis,cossacklabs/themis,cossacklabs/themis,cossacklabs/themis,cossacklabs/themis,cossacklabs/themis