fix #2781, ensure that the task that handles an error actually has an active handler
fix #2778, improve dataflow of finally blocks
fix #2779, chained comparisons doc
move collect() to general collections section
a couple doc fixes related to immutability
document immutable types. closes #2565
Merge pull request #2783 from staticfloat/usesystemrmath

Introduce USE_SYSTEM_RMATH to allow for system-packaged Rmath
fix #2784
Add in script files for doing nightly builds of julia, so any and all can use them