Made double-click miniaturize respect window settings

Previously, if the window was set to not allow miniaturizing,
double-clicking on the title would still work and miniaturize the
window.

Using performMiniaturize: instead of miniaturize: seems to fix this and
not allow miniturization when the window does not support it.
Merge pull request #123 from Kapeli/master

Made double-click miniaturize respect window settings
Fix Markdown syntax
Private content view class to dramatically speed up window resizing.
added documentation for 'showProxyIcon' property
showsProxyIcon declaration
override setRepresentedURL: in case the proxy icon should not be drawn
documentation update, my mistake: default for 'showsProxyIcon' is NO
renaming property to 'showsDocumentProxyIcon'
Merge pull request #126 from ByteProject/master

NSDoc / showsProxyIcon implementation
Coding style fixes.

Signed-off-by: Max Seelemann <max@the-soulmen.com>
Fixed setting an invalid frame when initially adding content views.
Swapping out content views removes previously set custom content view class.
Merge pull request #125 from macguru/master

Private content view class to speed up window resizing.
Style
Fix implicit value conversion.
Merge pull request #127 from rastersize/floorf-to-floor

Fix implicit value conversion.