Updated README.
Updated LfW interpreter to use project directory as current one (fixes #276).

Added `lfw.chdirtofile` option to use the current file directory (not the
project directory) as the current one.
Fixed `calltip` attribute to use/enable proper style.
Removed `calltipbg` attribute as it's replaced by `calltip.bg`.
Changed the order of applying styles to apply the main style last.
Added `auxwindow` attribute to style auxiliary windows.
Updated scheme picker to apply styles to all windows.
Fixed lunching zbstudio from folders with spaces; thanks to @Asmageddon.
Fixed handling of getenv returning general message (Mobdebug v0.5511).

Some environments return an error message ("getenv is not supported"),
which needs to be handled when a port number is expected.
Updated Corona API for v2014.2189.
Updated Marmalade Quick API for v7.2.
Fixed hiding calltip and auto-complete when switching between tabs on OSX.

Added manual call for KILL_FOCUS, which doesn't seem to be called on OSX
because of this wxwidgets issue (http://trac.wxwidgets.org/ticket/14269).
Fixed removing focus from editor when IDE loses focus on OSX (ref #204).

This helps with CPU utilization and canceling tooltips after switching
to other controls in the IDE and then switching to a different app.
Disabled singleinstance check by default on OSX (ref #204).

The singleinstance check is handled by OSX itself. In those rare cases
when the check in the IDE needed, it can be enabled by setting
`singleinstance = true` in the config.
Reduced the number of inactivity checks and timer calls (ref #204).
Fixed shortcut menu generator to display default shortcuts.
Added version dependency check for loaded plugins.
Updated AddConfig/RemoveConfig to refresh styles after changes (ref #166).
Added explicit focus for Find field in the find dialog on OSX.
Updated CHANGELOG for 0.50.