distinct URI for suspend/delete

/users/?suspend=<username>  =>  /users/suspend/<username>
/users/?delete=<username>   =>  /users/delete/<username>
added possibility to delete users
added granting/revoking of admin privileges

any admin (username 'admin' or account_type 'admin') can toggle the
account_type of any other non-guest user from 'admin' to 'user' and vice-versa
the "real" admin (username 'admin') is of course unaffected
Merge branch 'master' into usermgmt
Merge branch 'master' into usermgmt
Merge branch 'master' into usermgmt
add temporary install docs for development of sagenb
Merge pull request #83 from ppurka/install-doc

add temporary install docs for development of sagenb
Merge branch 'master' into usermgmt
translate new sass styles into css
change selector to only allow evaluation on active eval_buttons
Merge pull request #85 from jsyeo/eval_button_clickable

make eval button clickable
Merge branch 'master' into usermgmt
Fix slider so that vmin=0,vmax=2,stepsize=1 allows middle setting
Merge pull request #89 from nbruin/patch-1

Fix slider so that vmin=0,vmax=2,stepsize=1 allows middle setting
Update sagenb/notebook/notebook.py

Add Fricas as one of the SYSTEMS options.
Make pyOpenSSL an optional dependency

See Sage trac #13385: http://trac.sagemath.org/sage_trac/ticket/13385

Basically we want to fail gracefully if pyOpenSSL isn't installed. This
commit preemptively turns off secure mode as soon as notebook() is
called if it detects pyOpenSSL is not installed. There is also a single
OpenSSL import in sagenb's own code, so I wrapped that as well just in
case.
Don't silently turn off HTTPS

Actually, rather than falling back to HTTP when HTTPS cannot be used, we
should just throw an exception. Otherwise, users may be misled into
thinking they are using HTTPS when they are in fact not.
convert images list to string *after* the jmol rendering tries to append to it
Use Mathjax's jsMath2jax extension to provide backwards compatibility with div/spans that have "math" class

Some worksheets have div/spans that delimit math, in the jsMath style, in the html annotations.  Those stopped working when we upgraded to MathJax.  For example, Rob Beezer's worksheets converted from his book had this issue.