Test upgrade of bootstrap to 2.3.2

Attempt to find the cause of a compile error when compiling LESS files
for bootstrap 2.3.2. The problem has to do with mixins.less and has the
root cause in a LESS commit
https://github.com/twitter/bootstrap/commit/6b9bb547bf275d8723d50b16fbb22ba9e334da39
(Move to new selector interpolation, supported from 1.3.1) .

OLD: -      (~".span@{index}") { .span(@index); }
NEW: +      .span@{index} { .span(@index); }