Fix "selectedOptions" binding bug

Fixes an error where the binding does not update non-observable property
values.
fixes #550
Remove build output files from repository.
Remove Windows build files. Rename linux files from -linux to .sh; the .sh extension means that Windows users can still run the build just by double-clicking the build script.
Run tests in Phantomjs after build (only if Phantomjs is available); Delete build output files first.
fix travis build script
don't need to run tests again in travis file; ensure build script fails if tests fail
add file so output directory exists; add gitignore so that build output files can't be added back in.
Allow build script to run from a different directory
Make css binding accept any class name (matches 2.1.0 behavior).
prevent applying bindings more than once to the same node
prevent overwriting computed observable properties from two-way bindings
Change error message for applying bindings multiple times.
Support jQuery 1.9+ by using 'parseHTML' instead of 'clean' where available
Update build instructions in readme
Fix typo in gitignore
Merge branch '761-build-improvements'
Merge pull request #796 from SteveSanderson/796-support-jquery-1-9

Support for jQuery 1.9
Add spec that fails if jQuery 1.8+ is referenced
Implement fix for #801