Auto completion menu triggers too frequently in react-mode, for example, the
completion menu will pop up right after user finishes typing a javascript
statement.
The root cause is that the 'company-minimum-prefix-length variable has been set
to 0 in "html" layer, which is used by "react" layer.
Overriding this variable to 2, as defined in "auto-completion" layer, will
resolve this issue.