Only write one byte at a time and try to write many more bytes overall.

Hopefully this addresses FreeBSD and Gentoo issues with this test.
Merge remote-tracking branch 'pyca/master' into wantwritetest-37+67
Merge pull request #76 from pyca/wantwritetest-37+67

Only write one byte at a time and try to write many more bytes overall.

On some platforms this does a better job of completely filling the send buffer - which is the goal.