Dicombrowser

A few new things:
* Should be compatible with Python 2.7 and 3.6+, and with PyQt 4 and 5
* Image and tag view placed in a horizontal split pane instead of tabs, look for the tab split bar on the right side of the image window
* Search feature for tags, uses Python regular expressions to match by name, tag number, or value

A few fixes and UI updates.

Initial public release of DicomBrowser. The zip file is the packaged Windows program, unzip the contents to a directory and run the executable, no Python install needed. The dmg file contains an OSX application which can be run on its own without a Python install. To install in Linux or as a Python library see the README file.