execv invocation fixes

Change-Id: I80e7100a834b7eca2d9c8560c221cffd41492f03
README: Update required SDK and NDK versions
update-binary: Fix 4.3+ version check

In Bug #194 a check for 4.3+ was added, but checking major and minor
separately would yield an incorrect result on e.g. v5.0.  Fix this.
Merge pull request #198 from cernekee/version-v1

Trivial fix for v4.3+ version check logic