website: Grammar tweak for veewee-to-packer docs

website: Update HTML characters for the <enter> command in Virtualbox builder documentation

This commit removes <, > and instead uses <,> to describe the
enter command in the boot command code block in virtualbox
builder documentation. Noticed this after fixing the VMware doc.

website: change color of text on selection

website: Update HTML characters for the <enter> command in VMware builder documentation

website: Fix typo in the Veewee to Packer doc page

Fix typo in README file.

builder/amazonebs: sleep between checks for ami create

This commit removes <, > and instead uses &lt;,&gt; to describe the
enter command in the boot command code block in vmware builder
documentation.

fixes #50

When verifying large files, the checksum would take a long time and
downloader would be nil. When the goroutine asked for progress,
it would raise a nil exception.

website: Fix typos in setup page

Fix typo in README.md